Analogs of pridopidine, their preparation and use

ABSTRACT

This invention provides an isolated compound having the structure: 
                         
or a salt thereof.
 
     The invention also provides for a process for preparing 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol, 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl) phenyl)piperidone, 1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane, (3R,4S)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol, 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide, 1-(2-methylpentyl)-4-(3-(methylsulfonyl)phenyl)piperidine, 4-(3-(methylsulfinyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridne, and 4-(3-(methylsulfonyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine. 
     This invention also provides an impurity or a salt thereof for use, as a reference standard to detect trace amounts of the impurity in a pharmaceutical composition comprising pridopidine or a pharmaceutically acceptable salt thereof. This invention further provides a process for producing a pridopidine drug product comprising obtaining a pridopidine drug substance and mixing the pridopidine drug substance with suitable excipients so as to produce the pridopidine drug product. This invention also provides a process for producing a pridopidine drug product. This invention also provides a process of distributing a pridopidine drug product.

This application claims the benefit of U.S. Provisional Application No.62/076,436, filed Nov. 6, 2014, and U.S. Provisional Application No.62/019,337, filed Jun. 30, 2014, the entire contents of which are herebyincorporated by reference herein.

Disclosures of the publications cited in this application in theirentireties are hereby incorporated by reference into this application inorder to more fully describe the state of the art as of the date of theinvention described herein.

BACKGROUND OF THE INVENTION

Pridopidine (ACR16, TV-7820, Huntexil) is a unique compound developedfor the treatment of patients with motor symptoms associated withHuntington's disease. Its chemical name is4-(3-(Methylsulfonyl)phenyl)-1-propylpiperidine, and its ChemicalRegistry number is 882737-42-0 (U.S. Publication No.US-2013-0267552-A1). Processes of synthesis of pridopidine and apharmaceutically acceptable salt thereof are disclosed in U.S. Pat. No.7,923,459. U.S. Pat. No. 6,903,120 disclosed pridopidine for thetreatment of Parkinson's disease, dyskinesias, dystonias, Tourette'sdisease, iatrogenic and non-iatrogenic psychoses and hallucinoses, moodand anxiety disorders, sleep disorder, autism spectrum disorder, ADHD,Huntington's disease, age-related cognitive impairment, and disordersrelated to alcohol abuse and narcotic substance abuse.

BRIEF SUMMARY OF THE INVENTION

This invention provides an isolated compound having the structure:

or a salt thereof.

This invention also provides a composition comprising pridopidine and acompound which has the structure:

or a salt thereof, wherein the ratio of the weight of the compoundrelative to the weight of the pridopidine in the composition is from99:1 to 1:99.

This invention also provides a composition comprising a compound havingthe structure:

or a salt thereof, wherein the composition is free of pridopidine or asalt thereof.

The invention also provides a pharmaceutical composition comprising anamount of pridopidine and at least one of Compound 1, Compound 2,Compound 3, Compound 4, Compound 5, Compound 6, and Compound 7 wherein

-   -   a) Compound 1 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   g) Compound 7 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method.

This invention also provides a process for preparing Compound 1comprising the step of oxidizing4-hydroxy-4-(3-(methylthio)phenyl)-1-propylpiperidin-1-ium chloride withan oxidizing agent to form Compound 1.

This invention also provides a process for preparing Compound 2comprising the steps of:

-   -   a) reacting 3-bromothioanisole with ethyl        3-(4-oxopiperidin-1-yl)propanoate to form        1-(3-hydroxy-3,3-bis(3-(methylthio)phenyl)propyl)-4-(3-(methylthio)phenyl)piperidin-4-ol,    -   b) dehydrating the        1-(3-hydroxy-3,3-bis(3-(methylthio)phenyl)propyl)-4-(3-(methylthio)phenyl)piperidin-4-ol        formed in step a) with a dehydrating agent to obtain        1-(3,3-bis(3-(methylthio)phenyl)allyl)-4-(3-(methylthio)phenyl)-1,2,3,6-tetrahydropyridine,    -   c) oxidizing the        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)        phenyl)-1,2,3,6-tetrahydropyridine formed in step b) with an        oxidizing agent to form        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)phenyl)-1,2,3,6-tetrahydropyridine,        and    -   d) hydrogenating the        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)        phenyl)-1,2,3,6-tetrahydropyridine formed in step c) with a        hydrogenating agent to form Compound 2.

This invention also provides a process for preparing Compound 3comprising the steps of:

-   -   a) reacting 3-bromo thiophenol and 1,4-dibromobutane to form        1,4-bis((3-bromophenyl)thio)butane,    -   b) oxidizing the 1,4-bis((3-bromophenyl)thio)butane formed in        step a) with an oxidizing agent to form        1,4-bis((3-bromophenyl)sulfonyl)butane,    -   c) reacting 4-pyridinylboronic acid with the        1,4-bis((3-bromophenyl)sulfonyl)butane formed in step b) to        obtain 1,4-bis((3-(pyridin-4-yl)phenyl)sulfonyl)butane,    -   d) reacting l-iodopropane with        1,4-bis((3-(pyridin-4-yl)phenyl)sulfonyl)butane formed in        step c) to form        4,4′-((butane-1,4-diyldisulfonyl)bis(3,1-phenylene))bis(1-propylpyridin-1-ium)iodide,    -   e) adding a reducing agent to        4,4′-((butane-1,4-diyldisulfonyl)bis(3,1-phenylene))bis(1-propylpyridin-1-ium)iodide        formed in step d) to form        1,4-bis((3-(1-propyl-1,2,3,6-tetrahydropyridin-4-yl)phenyl)sulfonyl)        butane, and    -   f) hydrogenating the        1,4-bis((3-(1-propyl-1,2,3,6-tetrahydropyridin-4-yl)phenyl)sulfonyl)        butane formed in step e) with a hydrogenating agent to obtain        Compound 3.

This invention also provides a process for preparing Compound 4comprising the steps of:

-   -   a) epoxidizing        4-(3-(methylsulfonyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine        with an epoxidizing agent to form        (1S,6S)-6-(3-(methylsulfonyl)phenyl)-3-propyl-7-oxa-3-azabicyclo[4.1.0]heptane,        and    -   b) nucleophilically opening the epoxide of the        (1S,6S)-6-(3-(methylsulfonyl)phenyl)-3-propyl-7-oxa-3-azabicyclo[4.1.0]heptane        of step a) with a nucleophile to obtain Compound 4.

This invention also provides a process for preparing Compound 5comprising the step of reacting pridopidine with a peroxide to obtainCompound 5.

This invention also provides a process for preparing Compound 6comprising the step of reacting 4-(3-(methylsulfonyl)phenyl)piperidinewith 1-chloro-2-methylpentane to obtain Compound 6.

This invention also provides a process for preparing Compound 7comprising the steps of:

-   -   a) dehydrating        4-hydroxy-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-1-ium        chloride with a dehydrating agent to form        4-(3-(methylthio)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin-1-ium        hydrogen sulfate,    -   b) oxidizing        4-(3-(methylthio)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin-1-ium        hydrogen sulfate of step b) with an oxidizing agent to form        Compound 7. In one embodiment, the dehydrating agent is a strong        acid, preferably sulphuric acid. In another embodiment, the        dehydrating agent is a strong acid. In another embodiment, the        dehydrating agent is sulphuric acid. In another embodiment, the        oxidizing agent is a peroxide, preferably hydrogen peroxide. In        another embodiment, the oxidizing agent is a peroxide. In        another embodiment, the oxidizing agent is hydrogen peroxide.

This invention also provides a process for testing whether a sample of acomposition comprising pridopidine contains an undesirable impuritywhich comprises the step of determining whether the sample contains acompound having the structure:

This invention also provides a process for producing a pridopidine drugproduct comprising obtaining a pridopidine drug substance and mixing thepridopidine drug substance with suitable excipients so as to produce thepridopidine drug product, wherein the pridopidine drug substancecomprises:

-   -   i) an amount of Compound 1 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 1, relative to the        concentration of pridopidine, or    -   ii) an amount of Compound 2 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 2, relative to the        concentration of pridopidine, or    -   iii) an amount of Compound 3 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 3, relative to the        concentration of pridopidine, or    -   iv) an amount of Compound 4 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 4, relative to the        concentration of pridopidine, or    -   v) an amount of Compound 5 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 5, relative to the        concentration of pridopidine, or    -   vi) an amount of Compound 6 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 6, relative to the        concentration of pridopidine.

This invention also provides a process for producing a pridopidine drugproduct for commercial sale comprising obtaining a batch of pridopidinedrug product that comprises:

-   -   i) an amount of Compound 1 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 1, relative        to the concentration of pridopidine, or    -   ii) an amount of Compound 2 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 2, relative        to the concentration of pridopidine, or    -   iii) an amount of Compound 3 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 3, relative        to the concentration of pridopidine, or    -   iv) an amount of Compound 4 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 4, relative        to the concentration of pridopidine, or    -   v) an amount of Compound 5 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 5, relative        to the concentration of pridopidine, or    -   vi) an amount of Compound 6 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 6, relative        to the concentration of pridopidine, and        preparing the batch of pridopidine drug product for commercial        sale.

This invention also provides a process of distributing a pridopidinedrug product comprising a pridopidine drug substance comprising,

-   -   a) obtaining the pridopidine drug product wherein the        pridopidine drug substance comprises:        -   i) an amount of Compound 1 in the pridopidine drug substance            that is not more than 0.15 area-% Compound 1, relative to            the concentration of pridopidine, or        -   ii) an amount of Compound 2 in the pridopidine drug            substance that is not more than 0.15 area-% Compound 2,            relative to the concentration of pridopidine, or        -   iii) an amount of Compound 3 in the pridopidine drug            substance that is not more than 0.15 area-% Compound 3,            relative to the concentration of pridopidine, or        -   iv) an amount of Compound 4 in the pridopidine drug            substance that is not more than 0.15 area-% Compound 4,            relative to the concentration of pridopidine, or        -   v) an amount of Compound 5 in the pridopidine drug substance            that is not more than 0.15 area-% Compound 5, relative to            the concentration of pridopidine, or        -   vi) an amount of Compound 6 in the pridopidine drug            substance that is not more than 0.15 area-% Compound 6,            relative to the concentration of pridopidine; and    -   b) distributing the pridopidine drug product comprising the        pridopidine drug substance.

This invention also provides a process of distributing a pridopidinedrug product comprising,

-   -   a) obtaining the pridopidine drug product that comprises:        -   i) an amount of Compound 1 in the pridopidine drug product            that is not more than 0.15 area-% Compound 1, relative to            the concentration of pridopidine, or        -   ii) an amount of Compound 2 in the pridopidine drug product            that is not more than 0.15 area-% Compound 2, relative to            the concentration of pridopidine, or        -   iii) an amount of Compound 3 in the pridopidine drug product            that is not more than 0.15 area-% Compound 3, relative to            the concentration of pridopidine, or        -   iv) an amount of Compound 4 in the pridopidine drug product            that is not more than 0.15 area-% Compound 4, relative to            the concentration of pridopidine, or        -   v) an amount of Compound 5 in the pridopidine drug product            that is not more than 0.15 area-% Compound 5, relative to            the concentration of pridopidine, or        -   vi) an amount of Compound 6 in the pridopidine drug product            that is not more than 0.15 area-% Compound 6, relative to            the concentration of pridopidine; and    -   b) distributing the pridopidine drug product.

This invention also provides an impurity or a salt thereof for use, as areference standard to detect trace amounts of the impurity in apharmaceutical composition comprising pridopidine or a pharmaceuticallyacceptable salt thereof, wherein the impurity is selected from the groupconsisting of Compound 1, Compound 2, Compound 3, Compound 4, Compound 5and Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidine,the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising pridopidine and the        diluent solution,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid, f) injecting into the HPLC the diluent        solution, the resolution solution, the standard solution, and        the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the sample solution,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidine,the method comprising

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising the impurity,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the standard        solutions,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidineand a pharmaceutically acceptable carrier, the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising pridopidine and the        diluent solution,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the sample solution,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidineand a pharmaceutically acceptable carrier, the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising the impurity,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the standard        solutions,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of treating a subject afflictedwith a neurodegenerative disease or a neurodegenerative disordercomprising administering to the subject the pharmaceutical composition.

This invention also provides a method of treating a subject afflictedwith Huntington's disease comprising administering to the subject thepharmaceutical composition.

This invention also provides a process for validating a batch of apharmaceutical product containing pridopidine or a pharmaceuticallyacceptable salt thereof and a pharmaceutically acceptable carrier fordistribution comprising:

-   -   a) determining the amount of at least one of Compound 1,        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6;        and    -   b) validating the batch for distribution only if        -   i) the batch is determined to have not more than 0.15 area-%            Compound 1, relative to the concentration of pridopidine, or        -   ii) the batch is determined to have not more than 0.15            area-% Compound 2, relative to the concentration of            pridopidine, or        -   iii) the batch is determined to have not more than 0.15            area-% Compound 3, relative to the concentration of            pridopidine, or        -   iv) the batch is determined to have not more than 0.15            area-% Compound 4, relative to the concentration of            pridopidine, or        -   v) the batch is determined to have not more than 0.15 area-%            Compound 5, relative to the concentration of pridopidine, or        -   vi) the batch is determined to have not more than 0.15            area-% Compound 6, relative to the concentration of            pridopidine.

This invention also provides a process for preparing a validatedpharmaceutical composition comprising pridopidine comprising:

-   -   a) obtaining a batch of pridopidine drug substance;    -   b) determining the amount of at least one of Compound 1,        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6;        and    -   c) preparing the pharmaceutical composition from the batch only        if        -   i) the batch is determined to have not more than 0.15%            Compound 1, relative to the concentration of pridopidine, or        -   ii) the batch is determined to have not more than 0.15%            Compound 2, relative to the concentration of pridopidine, or        -   iii) the batch is determined to have not more than 0.15%            Compound 3, relative to the concentration of pridopidine, or        -   iv) the batch is determined to have not more than 0.15%            Compound 4, relative to the concentration of pridopidine, or        -   v) the batch is determined to have not more than 0.15%            Compound 5, relative to the concentration of pridopidine, or        -   vi) the batch is determined to have not more than 0.15%            Compound 6, relative to the concentration of pridopidine.

This invention also provides a process for preparing a pharmaceuticalcomposition comprising pridopidine, comprising

-   -   a) obtaining a batch of pridopidine drug product;    -   b) performing stability testing with a sample of the batch;    -   c) determining the total amount of at least one of Compound 1,        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6        in the sample of the batch after stability testing by an HPLC        method; and    -   d) preparing the pharmaceutical composition from the batch after        stability testing if the sample of the batch after stability        testing contains:        -   i) not more than 0.15% Compound 1, relative to the            concentration of pridopidine, or        -   ii) not more than 0.15% Compound 2, relative to the            concentration of pridopidine, or        -   iii) not more than 0.15% Compound 3, relative to the            concentration of pridopidine, or        -   iv) not more than 0.15% Compound 4, relative to the            concentration of pridopidine, or        -   v) not more than 0.15% Compound 5, relative to the            concentration of pridopidine, or        -   vi) not more than 0.15% Compound 6, relative to the            concentration of pridopidine.

This invention also provides an isolated compound having the structure:

or a salt thereof.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1: Typical Chromatogram of the control sample 1a,

FIG. 2: Typical Chromatogram of the control sample 2b.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides an isolated compound having the structure:

or a salt thereof.

In an embodiment of the present invention, the isolated compound has thestructure:

or a salt thereof.

In an embodiment, the isolated compound has the structure:

or a salt thereof.

In an embodiment, the isolated compound has the structure:

or a salt thereof.

In an embodiment, the isolated compound has the structure:

or a salt thereof.

In an embodiment, the isolated compound has the structure:

or a salt thereof.

This invention also provides a composition comprising pridopidine and acompound which has the structure:

or a salt thereof, wherein the ratio of the weight of the compoundrelative to the weight of the pridopidine in the composition is from99:1 to 1:99.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the ratio of the weight of the compound relative tothe weight of the pridopidine in the composition is from 90:10 to 10:90or 85:15 or 15:85.

This invention also provides a composition comprising a compound havingthe structure:

or a salt thereof, wherein the composition is free of pridopidine or asalt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

In an embodiment, the compound has the structure:

or a salt thereof.

The invention also provides a pharmaceutical composition comprising anamount of pridopidine and at least one of Compound 1, Compound 2,Compound 3, Compound 4, Compound 5, Compound 6, and Compound 7 wherein

-   -   a) Compound 1 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   g) Compound 7 is present in the pharmaceutical composition in an        amount not more than 10 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method.

In an embodiment,

-   -   a) Compound 1 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount not more than 0.15 area-% relative to the concentration        of pridopidine, based on a determination by an HPLC method.

In another embodiment,

-   -   a) Compound 1 is present in the pharmaceutical composition in an        amount greater than 0.01 area-%, and not more than 0.15 area-%        relative to the concentration of pridopidine, based on a        determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount greater than 0.01 area-%, and not more than 0.15 area-%,        relative to the concentration of pridopidine, based on a        determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount greater than 0.03 area-%, and not more than 0.15 area-%,        relative to the concentration of pridopidine, based on a        determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount greater than 0.01 area-%, and not more than 0.15 area-%,        relative to the concentration of pridopidine, based on a        determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount greater than 0.01 area-%, and not more than 0.15 area-%,        relative to the concentration of pridopidine, based on a        determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount greater than 0.01 area-% and not more than 0.15 area-%,        relative to the concentration of pridopidine, based on a        determination by an HPLC method.

In another embodiment,

-   -   a) Compound 1 is present in the pharmaceutical composition in an        amount less than 0.04 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount less than 0.05 area %, relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount less than 0.05 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount less than 0.04 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount less than 0.04 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount less than 0.04 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method.

In another embodiment,

-   -   a) Compound is present in the pharmaceutical composition in an        amount less than 0.01 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   b) Compound 2 is present in the pharmaceutical composition in an        amount less than 0.01 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   c) Compound 3 is present in the pharmaceutical composition in an        amount less than 0.03 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   d) Compound 4 is present in the pharmaceutical composition in an        amount less than 0.01 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   e) Compound 5 is present in the pharmaceutical composition in an        amount less than 0.01 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method, or    -   f) Compound 6 is present in the pharmaceutical composition in an        amount less than 0.01 area-% relative to the concentration of        pridopidine, based on a determination by an HPLC method.

In one embodiment, at least two of Compound 1, Compound 2, Compound 3,Compound 4, Compound 5 and Compound 6 are present. In anotherembodiment, at least three of Compound 1, Compound 2, Compound 3,Compound 4, Compound 5 and Compound 6 are present. In anotherembodiment, at least four of Compound 1, Compound 2, Compound 3,Compound 4, Compound 5 and Compound 6 are present. In anotherembodiment, least five of Compound 1, Compound 2, Compound 3, Compound4, Compound 5 and Compound 6 are present. In another embodiment,Compound 1, Compound 2, Compound 3, Compound 4, Compound 5 and Compound6 are present. In another embodiment, at least Compound is present. Inanother embodiment, at least Compound 3 is present. In anotherembodiment, at least Compound 4 is present.

In one embodiment, the pharmaceutical composition comprises pridopidinehydrochloride salt.

In an embodiment, the pharmaceutical composition is in the form of acapsule, a tablet, or a liquid suspension. In another embodiment, thepharmaceutical composition is in an oral dosage unit form.

In an embodiment, the pharmaceutical composition the oral dosage unitform comprises between 22.5-315 mg pridopidine. In another embodiment,the oral dosage unit form comprises between 45-250 mg pridopidine. Inanother embodiment, the oral dosage unit form comprises between 45-135mg pridopidine. In another embodiment, the oral dosage unit formcomprises between 90-315 mg pridopidine. In another embodiment, the oraldosage unit form comprises about 22.5 mg pridopidine. In anotherembodiment, the oral dosage unit form comprises about 45 mg pridopidine.In another embodiment, the oral dosage unit form comprises about 67.5 mgpridopidine. In another embodiment the oral dosage unit form comprisesabout 90 mg pridopidine. In another embodiment, the oral unit dosageform comprises about 100 mg pridopidine. In another embodiment, the oraldosage unit form comprises about 112.5 mg pridopidine. In anotherembodiment, the oral dosage unit form comprises about 125 mgpridopidine. In another embodiment, the oral dosage unit form comprisesabout 135 mg pridopidine. In another embodiment, the oral dosage unitform comprises about 150 mg pridopidine. In another embodiment, the oraldosage unit form comprises about 180 mg pridopidine. In anotherembodiment, the oral dosage unit form comprises about 200 mgpridopidine. In another embodiment, the oral dosage unit form comprisesabout 250 mg pridopidine. In another embodiment, the oral dosage unitform comprises about 315 mg pridopidine. In another embodiment, the oraldosage unit form is prepared for once daily administration. In anotherembodiment, the oral dosage unit form is prepared for more than oncedaily administration.

This invention also provides a process for preparing Compound 1comprising the step of oxidizing4-hydroxy-4-(3-(methylthio)phenyl)-1-propylpiperidin-1-ium chloride withan oxidizing agent to form Compound 1. In one embodiment, the oxidizingagent is a peroxide, preferably hydrogen peroxide. In anotherembodiment, the oxidizing agent is a peroxide. In another embodiment,the oxidizing agent is hydrogen peroxide.

This invention also provides a process for preparing Compound 2comprising the steps of:

-   -   a) reacting 3-bromothioanisole with ethyl        3-(4-oxopiperidin-1-yl)propanoate to form        1-(3-hydroxy-3,3-bis(3-(methylthio)phenyl)propyl)-4-(3-(methylthio)phenyl)piperidin-4-ol,    -   b) dehydrating the        1-(3-hydroxy-3,3-bis(3-(methylthio)phenyl)propyl)-4-(3-(methylthio)phenyl)piperidin-4-ol        formed in step a) with a dehydrating agent to obtain        1-(3,3-bis(3-(methylthio)phenyl)allyl)-4-(3-(methylthio)phenyl)-1,2,3,6-tetrahydropyridine,    -   c) oxidizing the        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)        phenyl)-1,2,3,6-tetrahydropyridine formed in step b) with an        oxidizing agent to form        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)phenyl)-1,2,3,6-tetrahydropyridine,        and    -   d) hydrogenating the        1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)        phenyl)-1,2,3,6-tetrahydropyridine formed in step c) with a        hydrogenating agent to form Compound 2.

In one embodiment, the dehydrating agent is a strong acid, preferablysulfuric acid. In one embodiment, the dehydrating agent is a strongacid. In another embodiment, the dehydration agent is sulfuric acid. Inanother embodiment, the oxidizing agent is a peroxide. In anotherembodiment, the oxidizing agent is hydrogen peroxide. In anotherembodiment, the hydrogenating agent is hydrogen.

This invention also provides a process for preparing Compound 3comprising the steps of:

-   -   a) reacting 3-bromo thiophenol and 1,4-dibromobutane to form        1,4-bis((3-bromophenyl)thio)butane,    -   b) oxidizing the 1,4-bis((3-bromophenyl)thio)butane formed in        step a) with an oxidizing agent to form        1,4-bis((3-bromophenyl)sulfonyl)butane,    -   c) reacting 4-pyridinylboronic acid with the        1,4-bis((3-bromophenyl)sulfonyl)butane formed in step b) to        obtain 1,4-bis((3-(pyridin-4-yl)phenyl)sulfonyl)butane,    -   d) reacting l-iodopropane with        1,4-bis((3-(pyridin-4-yl)phenyl)sulfonyl)butane formed in        step c) to form        4,4′-((butane-1,4-diyldisulfonyl)bis(3,1-phenylene))bis(1-propylpyridin-1-ium)iodide,    -   e) adding a reducing agent to        4,4′-((butane-1,4-diyldisulfonyl)bis(3,1-phenylene))bis(1-propylpyridin-1-ium)iodide        formed in step d) to form        1,4-bis((3-(1-propyl-1,2,3,6-tetrahydropyridin-4-yl)phenyl)sulfonyl)        butane, and    -   f) hydrogenating the        1,4-bis((3-(1-propyl-1,2,3,6-tetrahydropyridin-4-yl)phenyl)sulfonyl)        butane formed in step e) with a hydrogenating agent to obtain        Compound 3.

In one embodiment, the oxidizing agent is a peroxide, preferablyhydrogen peroxide. In another embodiment, the oxidizing agent is aperoxide. In another embodiment, the oxidizing agent is hydrogenperoxide. In another embodiment, the reducing agent is sodiumborohydride. In another embodiment, the hydrogenating agent is hydrogen.

This invention also provides a process for preparing Compound 4comprising the steps of:

-   -   a) epoxidizing        4-(3-(methylsulfonyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine        with an epoxidizing agent to form        (1S,6S)-6-(3-(methylsulfonyl)phenyl)-3-propyl-7-oxa-3-azabicyclo[4.1.0]heptane,        and    -   b) nucleophilically opening the epoxide of the        (1S,6S)-6-(3-(methylsulfonyl)phenyl)-3-propyl-7-oxa-3-azabicyclo[4.1.0]heptane        of step a) with a nucleophile to obtain Compound 4.

In one embodiment, the epoxidizing agent is sodium bromate. In anotherembodiment, the nucleophile is hydrogen.

This invention also provides a process for preparing Compound 5comprising the step of reacting pridopidine with a peroxide to obtainCompound 5. In one embodiment, the peroxide is hydrogen peroxide.

This invention also provides a process for preparing Compound 6comprising the step of reacting 4-(3-(methylsulfonyl)phenyl)piperidinewith 1-chloro-2-methylpentane to obtain Compound 6.

This invention also provides a process for preparing Compound 7comprising the steps of:

-   -   a) dehydrating        4-hydroxy-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-1-ium        chloride with a dehydrating agent to form        4-(3-(methylthio)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin-1-ium        hydrogen sulfate,    -   b) oxidizing        4-(3-(methylthio)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin-1-ium        hydrogen sulfate of step b) with an oxidizing agent to form        Compound 7.

In one embodiment, the dehydrating agent is a strong acid, preferablysulphuric acid. In another embodiment, the dehydrating agent is a strongacid. In another embodiment, the dehydrating agent is sulphuric acid. Inanother embodiment, the oxidizing agent is a peroxide, preferablyhydrogen peroxide. In another embodiment, the oxidizing agent is aperoxide. In another embodiment, the oxidizing agent is hydrogenperoxide.

This invention also provides a process for testing whether a sample of acomposition comprising pridopidine contains an undesirable impuritywhich comprises the step of determining whether the sample contains acompound having the structure:

This invention also provides a process for producing a pridopidine drugproduct comprising obtaining a pridopidine drug substance and mixing thepridopidine drug substance with suitable excipients so as to produce thepridopidine drug product, wherein the pridopidine drug substancecomprises:

-   -   i) an amount of Compound 1 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 1, relative to the        concentration of pridopidine, or    -   ii) an amount of Compound 2 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 2, relative to the        concentration of pridopidine, or    -   iii) an amount of Compound 3 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 3, relative to the        concentration of pridopidine, or    -   iv) an amount of Compound 4 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 4, relative to the        concentration of pridopidine, or    -   v) an amount of Compound 5 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 5, relative to the        concentration of pridopidine, or    -   vi) an amount of Compound 6 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 6, relative to the        concentration of pridopidine.

In one embodiment, the process further comprises determining the amountof the at least one of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the pridopidine drug substance. In anotherembodiment, the process further comprises determining the amount of theat least two of Compound 1, Compound 2, Compound 3, Compound 4, Compound5, and Compound 6 in the pridopidine drug substance. In anotherembodiment, the process further comprises determining the amount of theat least three of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the pridopidine drug substance. In anotherembodiment, the process further comprises determining the amount of theat least four of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the pridopidine drug substance. In anotherembodiment, the process further comprises determining the amount of theat least five of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the pridopidine drug substance. In anotherembodiment, the process further comprises determining the amount ofCompound 1, Compound 2, Compound 3, Compound 4, Compound 5, and Compound6 in the pridopidine drug substance. In another embodiment, the processfurther comprises subjecting a sample of the pridopidine drug substanceto stability testing before the step of determining the amount of the atleast one of Compound 1, Compound 2, Compound 3, Compound 4, Compound 5,and Compound 6 in the pridopidine drug substance.

This invention also provides a process for producing a pridopidine drugproduct for commercial sale comprising obtaining a batch of pridopidinedrug product that comprises:

-   -   i) an amount of Compound 1 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 1, relative        to the concentration of pridopidine, or    -   ii) an amount of Compound 2 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 2, relative        to the concentration of pridopidine, or    -   iii) an amount of Compound 3 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 3, relative        to the concentration of pridopidine, or    -   iv) an amount of Compound 4 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 4, relative        to the concentration of pridopidine, or    -   v) an amount of Compound 5 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 5, relative        to the concentration of pridopidine, or    -   vi) an amount of Compound 6 in the batch of pridopidine drug        product that is not more than 0.15 area-% Compound 6, relative        to the concentration of pridopidine, and        preparing the batch of pridopidine drug product for commercial        sale.

In an embodiment, the process further comprises determining the amountof the at least one of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the batch of pridopidine drug product. Inanother embodiment, the process further comprises determining the amountof the at least two of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the batch of pridopidine drug product. Inan embodiment, the process further comprises determining the amount ofthe at least three of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the batch of pridopidine drug product. Inan embodiment, the process further comprises determining the amount ofthe at least four of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the batch of pridopidine drug product. Inan embodiment, the process further comprises determining the amount ofthe at least five of Compound 1, Compound 2, Compound 3, Compound 4,Compound 5, and Compound 6 in the batch of pridopidine drug product. Inan embodiment, the process further comprises determining the amount ofCompound 1, Compound 2, Compound 3, Compound 4, Compound 5, and Compound6 in the batch of pridopidine drug product. In another embodiment, theprocess further comprises subjecting a sample of the batch ofpridopidine drug product to stability testing before determining theamount of the at least one of Compound 1, Compound 2, Compound 3,Compound 4, Compound 5, and Compound 6 in the sample of the batch ofpridopidine drug product.

This invention also provides a process of distributing a pridopidinedrug product comprising a pridopidine drug substance comprising,

a) obtaining the pridopidine drug product wherein the pridopidine drugsubstance comprises:

-   -   i) an amount of Compound 1 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 1, relative to the        concentration of pridopidine, or    -   ii) an amount of Compound 2 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 2, relative to the        concentration of pridopidine, or    -   iii) an amount of Compound 3 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 3, relative to the        concentration of pridopidine, or    -   iv) an amount of Compound 4 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 4, relative to the        concentration of pridopidine, or    -   v) an amount of Compound 5 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 5, relative to the        concentration of pridopidine, or    -   vi) an amount of Compound 6 in the pridopidine drug substance        that is not more than 0.15 area-% Compound 6, relative to the        concentration of pridopidine; and        b) distributing the pridopidine drug product comprising the        pridopidine drug substance.

This invention also provides a process of distributing a pridopidinedrug product comprising,

-   -   a) obtaining the pridopidine drug product that comprises:        -   i) an amount of Compound 1 in the pridopidine drug product            that is not more than 0.15 area-% Compound 1, relative to            the concentration of pridopidine, or        -   ii) an amount of Compound 2 in the pridopidine drug product            that is not more than 0.15 area-% Compound 2, relative to            the concentration of pridopidine, or        -   iii) an amount of Compound 3 in the pridopidine drug product            that is not more than 0.15 area-% Compound 3, relative to            the concentration of pridopidine, or        -   iv) an amount of Compound 4 in the pridopidine drug product            that is not more than 0.15 area-% Compound 4, relative to            the concentration of pridopidine, or        -   v) an amount of Compound 5 in the pridopidine drug product            that is not more than 0.15 area-% Compound 5, relative to            the concentration of pridopidine, or        -   vi) an amount of Compound 6 in the pridopidine drug product            that is not more than 0.15 area-% Compound 6, relative to            the concentration of pridopidine; and            b) distributing the pridopidine drug product.

This invention also provides an impurity or a salt thereof for use, as areference standard to detect trace amounts of the impurity in apharmaceutical composition comprising pridopidine or a pharmaceuticallyacceptable salt thereof, wherein the impurity is selected from the groupconsisting of Compound 1, Compound 2, Compound 3, Compound 4, Compound 5and Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidine,the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising pridopidine and the        diluent solution,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9,0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the sample solution,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidine,the method comprising

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising the impurity,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the standard        solutions,    -   wherein the impurity is Compound 1. Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidineand a pharmaceutically acceptable carrier, the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising pridopidine and the        diluent solution,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the sample solution,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of determining the concentrationof an impurity in a pharmaceutical composition comprising pridopidineand a pharmaceutically acceptable carrier, the method comprising,

-   -   a) preparing a sample solution from the pharmaceutical        composition,    -   b) preparing a diluent solution comprising methanol and water,    -   c) preparing a standard solution comprising the impurity,    -   d) preparing a resolution solution comprising pridopidine and        the impurity,    -   e) preparing a buffer solution by dissolving ammonium formate in        water and adjusting to pH of 9.0±0.10 with aqueous ammonia        hydroxide or formic acid,    -   f) injecting into the HPLC the diluent solution, the resolution        solution, the standard solution, and the sample solution,    -   g) running the HPLC using ultraviolet absorption at 190-400 nm        or 268 nm and a mixture of the buffer solution, methanol and        water as the mobile phase,    -   h) determining the retention time (RT) and the areas of the        peaks of the impurity in the chromatograms of the sample        solution, and    -   i) performing quantitation of the impurity with respect to the        corresponding peaks in the chromatograms of the standard        solutions,    -   wherein the impurity is Compound 1, Compound 2, Compound 3,        Compound 4, Compound 5 or Compound 6.

This invention also provides a method of treating a subject afflictedwith a neurodegenerative disease or a neurodegenerative disordercomprising administering to the subject the pharmaceutical composition.

This invention also provides a method of treating a subject afflictedwith Huntington's disease comprising administering to the subject thepharmaceutical composition.

This invention also provides a process for validating a batch of apharmaceutical product containing pridopidine or a pharmaceuticallyacceptable salt thereof and a pharmaceutically acceptable carrier fordistribution comprising:

-   -   a) determining the amount of at least one of Compound 1,        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6;        and    -   b) validating the batch for distribution only if        -   i) the batch is determined to have not more than 0.15 area-%            Compound 1, relative to the concentration of pridopidine, or        -   ii) the batch is determined to have not more than 0.15            area-% Compound 2, relative to the concentration of            pridopidine, or        -   iii) the batch is determined to have not more than 0.15            area-% Compound 3, relative to the concentration of            pridopidine, or        -   iv) the batch is determined to have not more than 0.15            area-% Compound 4, relative to the concentration of            pridopidine, or        -   v) the batch is determined to have not more than 0.15 area-%            Compound 5, relative to the concentration of pridopidine, or        -   vi) the batch is determined to have not more than 0.15            area-% Compound 6, relative to the concentration of            pridopidine.

This invention also provides a process for preparing a validatedpharmaceutical composition comprising pridopidine comprising:

-   -   a) obtaining a batch of pridopidine drug substance;    -   b) determining the amount of at least one of Compound 1,        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6;        and    -   c) preparing the pharmaceutical composition from the batch only        if        -   i) the batch is determined to have not more than 0.15%            Compound 1, relative to the concentration of pridopidine, or        -   ii) the batch is determined to have not more than 0.15%            Compound 2, relative to the concentration of pridopidine, or        -   iii) the batch is determined to have not more than 0.15%            Compound 3, relative to the concentration of pridopidine, or        -   iv) the batch is determined to have not more than 0.1            Compound 4, relative to the concentration of pridopidine, or        -   v) the batch is determined to have not more than 0.15%            Compound 5, relative to the concentration of pridopidine, or        -   vi) the batch is determined to have not more than 0.15%            Compound 6, relative to the concentration of pridopidine.

This invention also provides a process for preparing a pharmaceuticalcomposition comprising pridopidine, comprising

-   -   a) obtaining a batch of pridopidine drug product;    -   b) performing stability testing with a sample of the batch;    -   c) determining the total amount of at least one of Compound 1.        Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6        in the sample of the batch after stability testing by an HPLC        method; and    -   d) preparing the pharmaceutical composition from the batch after        stability testing if the sample of the batch after stability        testing contains:        -   i) not more than 0.15% Compound 1, relative to the            concentration of pridopidine, or        -   ii) not more than 0.15% Compound 2, relative to the            concentration of pridopidine, or        -   iii) not more than 0.15% Compound 3, relative to the            concentration of pridopidine, or        -   iv) not more than 0.15% Compound 4, relative to the            concentration of pridopidine, or        -   v) not more than 0.15% Compound 5, relative to the            concentration of pridopidine, or        -   vi) not more than 0.15% Compound 6, relative to the            concentration of pridopidine.

In an embodiment, the process further comprising step distributing thebatch if in step d) the batch is validated for distribution.

This invention also provides an isolated compound having the structure:

or a salt thereof.

Each embodiment disclosed herein is contemplated as being applicable toeach of the other disclosed embodiments. Thus, all combinations of thevarious elements described herein are within the scope of the invention.

For example, the elements recited in the packaging and pharmaceuticalcomposition embodiments can be used in the method and use embodimentsdescribed herein.

Terms

As used herein, and unless stated otherwise, each of the following termsshall have the definition set forth below.

As used herein, “pridiopidine” means pridopidine base or apharmaceutically acceptable salt thereof, including pridopidinehydrochloride. Preferably, in any embodiments of the invention asdescribed herein, the pridopidine is in the form of its hydrochloridesalt.

As used herein, “drug substance” refers to the active ingredient in adrug product or to the composition containing the active ingredientbefore it is formulated into in a drug product, which providespharmacological activity or other direct effect in the diagnosis, cure,mitigation, treatment, or prevention of disease, or to affect thestructure or any function of the body of man or animals.

As used herein, “drug product” refers to the formulated or finisheddosage form containing the drug substance as well as at least onepharmaceutically acceptable carrier.

As used herein, an “isolated” compound is a compound isolated from thecrude reaction mixture following an affirmative act of isolation. Theact of isolation involves separating the compound from the other knowncomponents of the crude reaction mixture, with some impurities, unknownside products and residual amounts of the other known components of thecrude reaction mixture permitted to remain. Purification is an exampleof an affirmative act of isolation.

As used herein, “stability testing” refers to tests conducted atspecific time intervals and various environmental conditions (e.g.,temperature and humidity) to see if and to what extent a drug productdegrades over its designated shelf life time. The specific conditionsand time of the tests are such that they accelerate the conditions thedrug product is expected to encounter over its shelf life. For example,detailed requirements of stability testing for finished pharmaceuticalsare codified in 21 C.F.R § 211.166, the entire content of which ishereby incorporated by reference.

As used herein, “about” in the context of a numerical value or rangemeans±10% of the numerical value or range recited.

As used herein, “approximately” in the context of a numerical value orrange means±5% of the numerical value or range recited or claimed.

As used herein, an “amount” of a compound as measured in milligramsrefers to the milligrams of compound present in a preparation,regardless of the form of the preparation. An “amount of compound whichis 40 mg” means the amount of the compound in a preparation is 40 mg,regardless of the form of the preparation. Thus, when in the form with acarrier, the weight of the carrier necessary to provide a dose of 40 mgcompound would be greater than 40 mg due to the presence of the carrier.

As used herein, “treating” and “treatment” encompasses. e.g., inducinginhibition, regression, or stasis of a disease, disorder or condition,or ameliorating or alleviating a symptom of a disease, disorder orcondition. “Ameliorating” or “alleviating” a condition or state as usedherein shall mean to relieve or lessen the symptoms of that condition orstate. “Inhibition” of disease progression or disease complication in asubject as used herein means preventing or reducing the diseaseprogression and/or disease complication in the subject.

“Administering to the subject” means the giving of, dispensing of, orapplication of medicines, drugs, or remedies to a subject to relieve,cure, or reduce the symptoms associated with a condition, e.g., apathological condition.

The drug substance of the present invention, e.g., pridopidinehydrochloride, may be administered in admixture with suitablepharmaceutical diluents, extenders, excipients, or carriers(collectively referred to herein as a pharmaceutically acceptablecarrier) suitably selected with respect to the intended form ofadministration and as consistent with conventional pharmaceuticalpractices. Capsules may contain suitable binders, lubricants,disintegrating agents, diluents, coloring agents, flow-inducing agents,and melting agents.

A dosage unit of the compounds used in the method of the presentinvention may comprise a single compound or mixtures thereof withadditional therapeutic agents.

A “dose” or “dosage unit” of pridopidine as measured in milligramsrefers to the milligrams of pridopidine hydrochloride present in apreparation, regardless of the form of the preparation. A dosage unitmay comprise a single compound or mixtures of compounds thereof. Adosage unit can be prepared for oral dosage forms, such as tablets,capsules, pills, powders, and granules. For example, the “dose” or“dosage unit” of priopidine may be 22.5, 45, or 67.5 mg.

As used herein, a “pharmaceutically acceptable” component is one that issuitable for use with humans and/or animals without undue adverse sideeffects (such as toxicity, irritation, and allergic response)commensurate with a reasonable benefit/risk ratio.

The subject invention is also intended to include all isotopes of atomsoccurring on the compounds disclosed herein, including impurities.Isotopes include those atoms having the same atomic number but differentmass numbers. By way of general example and without limitation, isotopesof hydrogen include tritium and deuterium. Isotopes of carbon includeC-13 and C-14.

As used herein, “detection limit” for an analytical method used inscreening or testing for the presence of a compound in a sample is athreshold under which the compound in a sample cannot be detected by theanalytical method used. The detection limits of a given HPLC method fordetecting an impurity in a sample containing pridopidine may vary basedon the method and the impurity or impurities being detected. Forexample, the detection limit of the typical HPLC method for detectingCompounds 1, 2, 4, 5 and 6 is 0.01 area-% and the detecting limit fordetecting Compound 3 is 0.03 area-%.

As used herein, “quantitation limit” for an analytical method used inscreening or testing for the presence of a compound in a sample is athreshold under which the compound in a sample cannot be quantified bythe analytical method used. The quantitation limits of a given HPLCmethod for detecting an impurity in a sample containing pridopidine mayvary based on the impurity or impurities being detected. For example,the quantitation limit of the typical HPLC method for quantifyingCompounds 1, 4, 5, and 6 is 0.04 area-% and the quantitation limit forCompound 3 is 0.05 area-%. The quantitation limit for Compound 2 is 0.05area-%.

A characteristic of a compound refers to any quality that a compoundexhibits, e.g., peaks or retention times, as determined by 1H nuclearmagnetic spectroscopy, mass spectroscopy, infrared, ultraviolet orfluorescence spectrophotometry, gas chromatography, thin layerchromatography, high performance liquid chromatography, elementalanalysis, Ames test, dissolution, stability and any other quality thatcan be determined by an analytical method. Once the characteristics of acompound are known, the information can be used to, for example, screenor test for the presence of the compound in a sample.

As used herein, “NMT” means no more than. As used herein, “LT” meansless than.

The amount of impurities are measured by reverse phase HPLC unlessotherwise specified.

As used herein, the term “effective amount” refers to the quantity of acomponent that is sufficient to yield a desired therapeutic responsewithout undue adverse side effects (such as toxicity, irritation, orallergic response) commensurate with a reasonable benefit/risk ratiowhen used in the manner of this invention, i.e. a therapeuticallyeffective amount. The specific effective amount will vary with suchfactors as the particular condition being treated, the physicalcondition of the patient, the type of mammal being treated, the durationof the treatment, the nature of concurrent therapy (if any), and thespecific formulations employed and the structure of the compounds or itsderivatives.

As used herein, “preparing drug product for commercial sale” means anactivity undertaken in preparation for commercial sale. Examplesinclude, but are not limited to, coloring, coding, stamping, packagingthe drug product.

It is understood that where a parameter range is provided, all integerswithin that range, and tenths thereof, are also provided by theinvention. For example, “20-40 mg” includes 20.0 mg, 20.1 mg, 20.2 mg,20.3 mg. etc. up to 40.0 mg.

Pharmaceutically Acceptable Salts

The active compounds for use according to the invention may be providedin any form suitable for the intended administration. Suitable formsinclude pharmaceutically (i.e. physiologically) acceptable salts, andpre- or prodrug forms of the compound of the invention.

Examples of pharmaceutically acceptable addition salts include, withoutlimitation, the non-toxic inorganic and organic acid addition salts suchas the hydrochloride, the hydrobromide, the nitrate, the perchlorate,the phosphate, the sulphate, the formate, the acetate, the aconate, theascorbate, the benzenesulphonate, the benzoate, the cinnamate, thecitrate, the embonate, the enantate, the fumarate, the glutamate, theglycolate, the lactate, the maleate, the malonate, the mandelate, themethane-sulphonate, the naphthalene-2-sulphonate, the phthalate, thesalicylate, the sorbate, the stearate, the succinate, the tartrate, thetoluene-p-sulphonate, and the like. Such salts may be formed byprocedures well known and described in the art.

Pharmaceutical Compositions

While the compounds for use according to the invention may beadministered in the form of the raw compound, it is preferred tointroduce the active ingredients, optionally in the form ofphysiologically acceptable salts, in a pharmaceutical compositiontogether with one or more adjuvants, excipients, carriers, buffers,diluents, and/or other customary pharmaceutical auxiliaries.

In an embodiment, the invention provides pharmaceutical compositionscomprising the active compounds or pharmaceutically acceptable salts orderivatives thereof, together with one or more pharmaceuticallyacceptable carriers therefore, and, optionally, other therapeutic and/orprophylactic ingredients know and used in the art. The carrier(s) mustbe “acceptable” in the sense of being compatible with the otheringredients of the formulation and not harmful to the recipient thereof.

Table 1 shows the structures of Compounds 1-8.

TABLE 1 Compound 1 Potential Impurity in pridopidine.

4-(3- (methylsulfonyl)phenyl)- 1-propylpiperidin-4-ol Compound 2Potential impurity of pridopidine.

1-(3,3-bis(3- (methylsulfonyl)phenyl) propyl)-4-(3- (methylsulfonyl)phenyl)piperidone Compound 3 Potential impurity in pridopidine.

1,4-bis((3-(1- propylpiperidin-4-yl) phenyl)sulfonyl)butane Compound 4Potential impurity in pridopidine.

(3R,4S)-4-(3- (methylsulfonyl)phenyl)- 1-propylpiperidin-3-ol Compound 5Potential impurity in pridopidine.

4-(3- (methylsulfonyl)phenyl)- 1-propylpiperidine 1-oxide Compound 6

1-(2-methylpentyl)-4-(3- (methylsulfonyl)phenyl) piperidine Compound 7

4-(3- (methylsulfinyl)phenyl)- 1-propyl-1,2,3,6- tetrahydropyridineCompound 8

4-(3- (methylsulfonyl)phenyl)- 1-propyl-1,2,3,6- tetrahydropyridine

This invention will understood by reference to the Experimental Detailswhich follow, but those skilled in the art will readily appreciate thatthe specific experiments detailed are only illustrative of the inventionas described more fully in the claims which follow thereafter.

Experimental Details

EXAMPLES Example 1—Preparation Of Compound 1(4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol)

To a suspension of4-hydroxy-4-(3-(methylthio)phenyl)-1-propylpiperidin-1-ium chloride (140g, 348 mmol) in 710 mL water were added 1.5 g sodium tungstatedihydrate, and the mixture was heated to 45° C. 102 mL of 33% H₂O₂ wereadded in 20 min at 45-55° C. The suspension dissolved after 20 mLaddition. The solution was then stirred at 48-51° C. for 30 min afterwhich HPLC showed no more starting material and two new peaks, one at RT2.68 min (823%) and the other at RT 3.66 min (11.8%). After additionalstirring for 2 hr and 45 min HPLC showed that the peak at RT 2.68 mindecreases to 7.5% and the peak at RT 3.66 min increases to 88.5%. Afteranother 45 min the mixture was cooled to 20° C. and into the reactionmixture were added 500 mL toluene and 150 mL-5M NaOH. After stirring for5 min the mixture was poured into separator funnel. The solubility ofthe product in toluene is low. Majority of the product settled as veryviscous liquid layer in the bottom. The water phase (and most of theproduct) was separated, toluene phase was washed successively with 5%Na₂SO₃ solution and with brine and dried on MgSO₄. The water phase wasextracted with 500 mL DCM. The organic phase was washed successivelywith 5% Na₂SO₃ solution and water and was dried on MgSO₄. Both extractswere concentrated on a rotavapor. 500 mL of heptanes were added to bothresidues, and the suspensions were stirred at room temperature for 2hrs. The precipitates were filtered, washed with heptane and dried. Fromthe DCM extract were obtained 83.8 g of white powder, purity by HPLC98.8%, 1H-NMR assay 97.9%. (From the toluene extract were obtained 13.7g of white powder, purity by HPLC 98.0%).

NMR Identity Analysis of Compound 1

The following data in Tables 2 and 3 was determined using a sample of78.95 mg Compound 1, a solvent of 0.55 ml DMSO-D6, 99.9 atom % D, andthe instrument was a Broker Avance III 400 MHz.

TABLE 2 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 8.07 1 t, J = 1.7 Hz H5H1^(b), H3^(b) C1, C3, C4^(b), C6^(b), C8 7.82 1 d, J = 7.9 Hz H3 H2,H5^(b) C1, C4^(b), C5, C8 7.79 1 d, J = 7.9 Hz H1 H2, H5^(b) C3, C4^(b),C5 7.59 1 t, J = 7.9 Hz H2 H1, H3 C3, C4, C5^(b), C6, C8^(b) 5.08 1 sH17 — C8, C9, C13 3.21 3 s H18 — C6^(b) 2.67 2 d, J = 11.5 Hz H10, H12H10, H12, C8^(b), C9^(b), C10, H13, H9 C12, C13^(b) 2.37 2 t, J = 11.6Hz H10, H12 H10, H12, C8^(b), C9^(b), C10, H13, H9 C12, C13^(b), C142.28 2 t, J = 7.3 Hz H14 H15 C10, C12. C15, C16 1.97 2 dt, J = 12.5 and4.1 Hz H9, H13 H10, H12, C9, C10, C12, H13, H9 C13 1.60 2 d, J = 12.8 HzH9, H13 H10, H12, C8, C9, C13 H13, H9 1.46 2 hex, J = 7.5 Hz H15 H14,H16 C14, C15 0.87 3 t, J = 7.5 Hz H16 H15 C14, C15 ^(a)The assignment isbased on the coupling pattern of the signals, coupling constants andchemical shifts. ^(b)Weak signal. ^(c)Spectra is calibrated by thesolvent residual peak (2.5 ppm).

TABLE 3 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 151.9 C4140.6 C6 130.1 C3 129.0 C2 124.9 C1 123.3 C5 70.0 C8 60.2 C14 49.0 C10,C12 43.6 C18 38.0 C9, C13 19.8 C15 12.0 C16 ^(a)The assignment is basedon the chemical shifts and 1H-13C couplings extracted from HSQC and HMBCexperiments. ^(b)Spectra is calibrated by a solvent peak (39.54 ppm)

Example 2—Preparation Of Compound 2(1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidine)

Preparation of ethyl 3-(4-oxopiperidin-1-yl)-propanoate (StartingMaterial for Compound 2)

Ethanol (1550 mL) was poured into a 4 L three-necked round-bottom flaskequipped with over-head stirring followed by the addition of 125 g (814mmol, 1 eq) 4-piperidone monohydrate hydrochloride and 225 g (1628 mmol,2 eq) potassium carbonate. Ethyl 3-chloropropanoate (111 g, 1 eq) wasadded and the reaction mixture was stirred for 3 h after which HPLCshowed that the product reached only 10% area. Another 0.5 eq of K₂CO₃was added (56.2 g) and stirring continued at 24° C. After total of 45 hthe product reached 86% area (HPLC). Another 0.2 eq of K₂CO₃ was addedand the reaction mixture was stirred for additional 4.5 h at 35° C.after which HPLC showed 96% area of the product. The mixture wasfiltered through a sintered glass filter, washed with 200 ml ethanol andconcentrated on vacuum to 156 g yellow colored oil that was distilledunder vacuum of 2 mmHg in 156° C. bath. The main fraction distilled at120° C. to yield 97.8 g (60%) of 99.3% area (HPLC).

Preparation of1-(3-hydroxy-3,3-bis(3-(methylthio)phenyl)propyl)-4-(3-(methylthio)phenyl)piperidin-4-ol (Compound 2, 1st Intermediate)

3-Bromothioanisole (170.3 g; 0.84 mol, 3.2 eq) and THF (700 mL) werecharged to a 2 L flask, stirred under nitrogen and cooled on dryice/acetone bath to −74° C. A solution of n-hexyllithium in hexane(2.3M; 237.4 g; 0.77 mol, 3.0 eq) was added and the reaction mixturebecame slightly yellowish. Stirring continued for additional 30 min at−74° C. A solution of ethyl 3-(4-oxopiperidin-1-yl)propanoate (50.2 g;0.26 mol, 1 eq) in THF (100 mL) was added during 1 h 15 min to thereaction mixture and the stirring continued for additional 30 min at−74° C. to give a yellow clear solution. The cooling stopped and thereaction warmed to −40° C. A solution of HCl (33%; 90 g, 0.82 mol, 3.1eq) in water (100 mL) was added dropwise for 20 min to give a lightyellow emulsion in +8° C. The light yellow organic phase was separated,washed with water (3×200 mL) and extracted twice with aqueous HCl (33%HCl 40 g/300 mL water) to give lower yellow phase (234 g). The organicupper light yellow phase was evaporated up to 159 g solution and theprecipitate formed during concentration was filtered to give 19.1 gyellow sticky precipitate. The precipitate was combined with the loweryellow phase, methanol (50 mL) and THF (200 mL) were added and distilled(67° C., 248 g distilled). Heptane (200 mL was added, the two liquidphase was stirred for 20 min at 40° C. and cooled to RT. The upperheptane phase was discarded and water (200 mL) was added to the viscousyellow residue water. After stirring stopped the colorless water wasdecanted to leave 182 g of very viscous light yellow residue (HPLC: 82%area).

Preparation of1-(3,3-bis(3-(methylthio)phenyl)allyl)-4-(3-(methylthio)phenyl)-1,2,3,6-tetrahydropyridine(Compound 2, 2nd Intermediate)

Into the viscous light yellow residue was added 2-propanol (200 mL) andthe reaction mixture was distilled at atmospheric pressure to give 200mL of azeotropic distillate, leaving dark yellow oil into which methanol(50 mL), 2-propanol (350 mL) and conc. sulfuric acid (36.5 g, 0.35 mol.1.35 eq) were added. The reaction mixture was heated for 26 hours(mixture temperature 81-84° C., vapor temperature 79° C.) and about 440mL of distillate were collected. At the end the temperature reached 87°C. and the reaction mixture was foaming. After cooling was added toluene(100 mL) and water (200 mL) and the reaction mixture was heated toreflux (87° C.). The heating stopped and after cooling three phases wereformed. The lower oily phase was washed with water (2×200 mL) andconcentrated by vacuum distillation to give dark yellow viscous residue.Water (300 mL) was added and the mixture was refluxed then cooled to 40°C. and water phase was decanted to leave about 200 g orange turbidliquid HPLC: 82% area) which was used in the next step.

Preparation of1-(3,3-bis(3-(methylsulfonyl)phenyl)allyl)-4-(3-(methylsulfonyl)phenyl)-1,2,3,6-tetrahydropyridine (Compound 2, 3rd Intermediate)

To the 200 g orange turbid liquid from the previous stage was added 500mL water, sodium tungstate dihydrate (2 g, 6 mmol) and concentratedsulfuric acid (20 mL). The mixture was heated to 35° C. and 33% H₂O₂ wasadded drop-wise in 1 h during which the yellow viscous mass on thebottom of the flask dissolved slowly and the temperature rose up to 55°C. then decreased slowly to 42° C. The reaction mixture was heated to50° C. for 2 hr and additional 32 g of 33% H₂O₂ were added. The reactioncontinued for another 4 h at 50° C. and additional 20 g of 33% H₂O₂ wereadded. After 2 h the reaction mixture was cooled down (25° C.) andalkalized to pH12 by 50% NaOH solution. Water (300 mL) was added andafter 20 min of mechanical stirring was discarded. Another 200 mL ofwater were added, stirred mechanically for 20 min and discarded to give158.2 g highly viscous yellow mass (HPLC: 75.4% area). This mass washeated for 30 min 4 times with butanol (200 mL@95° C., 200 mL@100° C.,400 mL@100° C. and 700 mL@114° C.) and twice with acetic acid (8 mL and250 mL@95° C.) to give light brown oil that was used in the next step(114.9 g, HPLC: 89% area).

Preparation of1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidine(Compound 2)

The light brown oil from the previous stage (114.9 g, HPLC: 89% area)was added into a 2 L autoclave with 550 mL acetic acid and 10% Pd/Ccatalyst (25 g, 23.5 mmol). Hydrogen was introduced (120 psi) and thereaction was heated to 90° C. for 16 h. After cooling, the catalyst wasfiltered, washed with acetic acid (50 ml) and the clear yellowishfiltrate was concentrated in vacuum to give 134 g brown viscous residue(HPLC: 82% area). Water (300 ml) was added, made alkaline (40% NaOH,pH>12) and extracted with 120 mL dichloromethane that afterconcentration gave 77.2 g brown sticky mass (HPLC: 83% area). Theresidue was treated with butanol (5×100 mL, 95° C.), cooled down and thebutanol phase over an oily phase was filtered. A total of 74.9 g solidphase was resulted which was dissolved in 200 mL acetone and the clearyellow solution was evaporated to give 70.1 g dark yellow clear viscousresidue. The residue was treated with heptane (2×100 mL, 95° C.) whichwas cooled and decanted. After evaporation in a rotavapor a pale yellowfoamy solid was obtained (65.1 g, HPLC: 84% area). The solid wasdissolved in 200 mL dichloromethane, 85 g silica was added and themixture was evaporated and loaded on 1.32 Kg silica gel column which waseluted by dichloromethane with 0.5-3.0% methanol and 0.5% trietylamine,Compound 2 was isolated to give 25.8 g, HPLC: 93.2% area, 1H-NMR assay:91.2%.

NMR Identity Analysis of Compound 2

The following data in Tables 4 and 5 was determined using a sample of62.03 mg Compound 2, a solvent of 0.6 ml CDCl₃, 99.8 atom % D, and theinstrument was a Bruker Avance III 400 MHz.

TABLE 4 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 7.87 2 s H20 H22^(b),H24^(b) C16, C21^(b), C22, C24 7.72-7.80 4 m H1, H5, H22 H2, H23 C1, C3,C5, C8, C20, C24 7.47-7.56 6 m H2, H3, H23, H1, H3, H20, C1, C4, C5, C6,C8, H24 H22 C16, C19, C21, C20, C22, C24^(b) 4.33 1 t, J = 7.1 Hz H16H15 C14^(b), C15, C19, C20, C24 3.05 9 s H18, H25 — — 2.94 4 d, J = 11.5Hz H10, H12 H10, H12, C8, C9^(b), C10, C12, H9, H13 C13^(b) 2.53-2.62 1m H8 H9, H13 C3^(b), C4, C5^(b), C9, C13, C10^(b), C12^(b) 2.24-2.34 4 mH14, H15 H16 C10, C12, C14, C15, C16, C19 2.02 2 t, J = 11.5 Hz H10,H12, H10, H12, C8, C9^(b), C10, C12, H9, H13 C13^(b), C14 1.72-1.85 4 mH9, H13 H8, H10, H12 C4^(b), C8, C9, C10^(b), C12^(b),C13 ^(a)Theassignment is based on the coupling pattern of the signals, couplingconstants and chemical shifts. ^(b)Weak signal. ^(c)Spectra iscalibrated by the solvent residual peak (7.28 ppm).

TABLE 5 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 148.0 C4145.5 C19 141.0 C21 140.6 C6 133.2 C24 132.3 C3 129.9 C23 129.5 C2 126.7C20 125.7 C22 125.6 C5 125.2 C1 55.9 C14 54.0 C10, C12 48.2 C16 44.51C18 44.48 C25 42.4 C8 32.3 C9, C13 31.8 C15 ^(a)The assignment is basedon the chemical shifts and 1H-13C couplings extracted from HSQC and HMBCexperiments. ^(b)Spectra is calibrated by a solvent peak (77.16 ppm)

Example 3—Preparation of Compound(1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane) Preparationof 1,4-bis((3-bromophenyl)thio)butane (Compound 3, 1st Int.)

KOH (56.2 g) was added into methanol (1200 mL) in 15 min. The clearsolution was cooled on water bath to 0° C. A solution of 3-bromothiophenol (150.2 g, 0.79 mol) in methanol (200 mL) was added in 50 minkeeping the temperature at 1-3° C. A solution of 1,4-dibromobutane (86.5g; 0.40 mol) in methanol (150 ml) was added in 40 min to give a yellowturbid mixture. After additional 4 hours stirring the reaction mixturebecame white turbid and it was stirred for additional 20 h at 25° C. Thesuspension was filtered and washed with water (3×100 mL) and methanol(2×100 mL) to give 239 g wet white solid that was dried to 163.6 g(94.6% yield, HPLC: 97.9%).

Preparation of 1,4-bis((3-bromophenyl)sulfonyl)butane (Compound 3, 2ndIntermediate)

To a solution of 1,4-bis-(3-bromophenylthio)-butane (155.0 g, 0.358 mol)in acetic acid (1500 mL) was added sodium tungstate dihydrate (2.5 g,0.0075 mol) and the suspension was heated on water-bath to 45° C. 50%H₂O₂ (300 mL, 5.28 mol) was added drop-wise into the reaction mixtureduring 3.5 h keeping the temperature at 45-55° C. The reaction mixturewas kept under stirring for additional 3 h at 45° C. and 16 h at 23° C.The off white slurry was filtered, washed with water (3×200 mL) anddried on air to give 179.6 g (99% crude yield, HPLC: 92.2% product, 7.1%by product). The crude product (175 g) was added to toluene (1400 mL)and heated to >85° C. for distillation. Distillation stopped when nomore water was distilled (180 mL toluene and 10 mL water). The clearreaction mixture was allowed to cool down and was filtered afterovernight stirring at ambient temperature. The bright colorless crystalswere washed (150 mL toluene) and dried to give 156.1 g product (86.7%yield, HPLC: product 96.0%, main by-product 3.5%).

Preparation of 1,4-bis((3-(pyridin-4-yl)phenyl)sulfonyl)butane (Compound3 3rd Intermediate)

To a solution of 1,4-Bis-((3-bromophenyl)-sulfonyl)-butane (92.0 g, 185mmol) and butanol (1.0 L) was added 4-pyridinylboronic acid (75.0 g, 610mmol), potassium carbonate (172 g, 1.24 mol) and the catalysttrans-dichlorobis-(triphenylphosphine) palladium (2.0 g; 2.8 mmol). Theviolet suspension was heated at stirring under nitrogen to 90-95° C.within 1 h. The reaction mixture became brown and heating continued formore 4 h. Additional 4-pyridinylboronic acid (3.5 g, 28 mmol) was addedand the reaction mixture heated up to 100° C. for 1 h. Heating stopped,water (600 mL) was added and the temperature dropped to 60° C. Theresulting dark gray suspension was stirred overnight at ambienttemperature and filtered (slowly). The filter cake was washed with water(100 mL) to give 153 g wet solid which was suspended in hot acetone (2×1L, 50° C.). The solid was then suspended with 0.5 L water at 65° C.followed by 2×1 L acetone suspension. The acetone solution were combinedand concentrated on a rotavapor to give 90.3 g pale yellow solid (yield:91%, HPLC: 91.8% area).

Preparation of4,4′-((butane-1,4-diyldisulfonyl)bis(3,1-phenylene))bis(1-propylpyridin-1-ium)iodide(Compound 3 4th Intermediate)

To a solution of 1,4-Bis-((3-(pyridin-4-yl)-phenyl)-sulfonyl)-butane(85.8 g, 160 mmol) and butanol (450 mL) was added 1-iodopropane (91.7 g,540 mmol). The stirring mixture was heated up to 90-95° C. in nitrogenatmosphere and kept at this temperature for 6 hours. The dark yellowslurry was then cooled down to room temperature and kept at thistemperature for 15 h. The yellow clear solution was then decanted andbutanol (300 mL) was added. The mixture was heated to 70° C. where itdissolved. Heating continued to 95° C. and light brown slurry appeared.The heating was stopped and the mixture cooled down to 40° C. The yellowcloudy liquid was decanted and a dark yellow solid mass was filtered togive 173.5 g (HPLC: 84% area) which was used as is in the next step.

Preparation of1,4-bis((3-(1-propyl-1,2,3,6-tetrahydropyridin-4-yl)phenyl)sulfonyl)butane (Compound 3, 5th Intermediate)

To the solid crude starting material (173.5 g from the previous stage)was added methanol (450 mL) and the mixture was heated to reflux to givedark yellowish red clear solution which after cooling gave two phases,the lower one weigh 150 g (HPLC: 88.4% area, yield corrected to area %:131 g, 157 mmol). Methanol (400 mL) was added and the mixture was cooled(0° C.). Sodium borohydride (23.75 g, 624 mmol, 4 eq) was added and thereaction mixture was allowed to warm to RT and stirred for additional 9h. The workup includes concentrating filtrates and precipitating frombutanol and methanol, several slurries in butanol, extraction by hotbutanol from water and finally active carbon treatment to the productdissolved in hot butanol to give 63.0 g (HPLC: 85% area) which was usedas is in the next step.

Preparation of 1,4-bis((3-(1-propylpiperidine-4yl)phenyl)sulfonyl)butane(Compound 3)

The product from the previous step (60.0 g, 51 g as HPLC is 85% area, 87mmol) was added into an autoclave with 350 mL acetic acid. A suspensionof 10% Pd/C catalyst (10 g, 9.4 mmol) in water (80 mL) was added. Airwas exchange to nitrogen and then hydrogen was introduced (150 psi) andthe reaction was heated to 85° C. for 6 h. After cooling the catalystwas filtered, washed with acetic acid (2×30 mL) and water (2×30 mL) andconcentrated under vacuum to give 98 g of slightly brownish viscousresidue. The residue was dissolved with water (200 mL), filtered (toremove traces of charcoal) and washed with 50 mL water. To the slightlybrownish solution was added concentrated NaOH up to pH 13 and themixture was stirred for 30 m. The massive precipitation was filtered togive 78.1 g slightly beige wet solid. The wet solid was mixed with water(100 mL) and toluene (300 mL), heated up to 87° C. for 30 min and thedark yellow water phase was separated. The organic phase was filteredand cooled down to 30° C. After 4 h the slurry was filtered, washed with20 mL toluene and dried to give 40.8 g off-white solid (HPLC: 74.4%area). The solid was then suspended in toluene (260 mL) and water (40mL) and heated up to 85° C. The colorless water phase was separated andthe toluene phase was filtered, cooled down to 5° C. for 2 hr andfiltered to give after drying 38.0 g off-white solid (HPLC: 81.5% area).The solid was then crystallized twice from toluene (300 mL, heating to90° C., cooled to 3° C., filtered, washed with 30 mL toluene, dried) togive 31.2 g. HPLC: 96.9% area, 1H-NMR assay: 93.9%.

NMR Identity Analysis of Compound 3

The following data in Tables 6 and 7 was determined using a sample of47.82 mg Compound 3, a solvent of 1.0 ml DMSO-D6, 99.9 atom % D, and theinstrument was a Bruker Avance III 400 MHz.

TABLE 6 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 7.68-7.70 2 m H5 H1^(b),H3^(b) C1, C3, C8 7.66 2 dt, J = 7.5 and 1.2 Hz H1 H5^(b), H2 C3, C57.63 2 d, J = 7.7 Hz H3 H2, H5^(b) C1, C5, C8 7.55 2 t, J = 7.5 Hz H2H1, H3 C1^(b), C3^(b), C4, C6 3.30-3.37 4 m H18 H19 C19 2.95 4 d, J =11.5 Hz H10, H12 H10, H12, C8^(b) H9, H13 2.61 2 t, J = 11.9 Hz H8 H9,H13 — 2.25 4 t, J = 7.2 Hz H14 H15 C10, C12, C15, C16 1.96 4 t, J = 11.9Hz H10, H12 H10, H12, — H9, H13 1.76 4 d, J = 12.6 Hz H9, H13 H8, H9,H10, — H12, H13 1.62-1.71 4 m H9, H13 H8, H9, H10, C10^(b), C12^(b),C9^(b), H12, H13 C13^(b) 1.59-1.65 4 m H19 H18 C19^(b) 1.43 4 sextet, J= 7.3 Hz H15 H14, H16 C14, C16 0.86 3 t, J = 7.2 Hz H16 H15 C14, C15^(a)The assignment is based on the coupling pattern of the signals,coupling constants and chemical shifts. Due to the low concentration ofdissolved material some expected HMBC signals were masked by backgroundnoise. ^(b)Weak signal. ^(c)Spectra is calibrated by the solventresidual peak (2.5 ppm).

TABLE 7 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 147.9 C6139.2 C4 132.2 C3 129.4 C2 125.7 C5 125.2 C1 60.2 C14 53.7 C10, C12, C1841.7 C8 32.8 C9, C13 20.7 C19 19.7 C15 11.9 C16 ^(a)The assignment isbased on the chemical shifts and 1H-13C couplings extracted from HSQCand HMBC experiments. ^(b)Spectra is calibrated by a solvent peak (39.54ppm).

Example 4—Preparation of Compound 4((3R,4S)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol)Preparation of(1S,6S)-6-(3-(methylsulfonyl)phenyl)-3-propyl-7-oxa-3-azabicyclo[4.1.0]heptane

Into a 4 L reactor was added at room temperature Compound 8 (229 g, 820mmol, 1 eq) and 2N sulfuric acid (1147 mL, 112 g sulfuric acid, 1.147mol, 1.4 eq). The reaction light yellow mixture was stirred and sodiumbromate (126 g, 836 mmol, 1.02 eq) was added. The mixture became yellowand the temperature dropped (endothermic dissolution). After 30 min thereaction temperature reached 35° C. and heated further to 40° C. for 6 hto give dark yellow solution with precipitate in the bottom of reactor.Toluene (2 L) and NaOH (24%, 546 g, 131 g NaOH. 3.28 mol, 4.0 eq) wereadded and the reaction mixture was vigorously stirred for 1 hour at 42°C. The reaction mixture was then poured into a 4 L separation funnel.The dark water phase was discarded and the dark red organic phase waswashed with 1.1 L 5% sodium sulphite solution and 1 L 20% brine. Theorganic phase was then concentrated on a rotavapor (50° C., 90-65 mbar,finally at 45 mbar) to give 111 g dark red oil with crystals in theflask. A GC analysis (5 mg red oil dissolved in 0.6 ml toluene) showed53% area product, 29% and 5.2% area unknown peaks and 0.4% Compound 8.The product goes to the reduction in the next stage.

Preparation of(3S,4R)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol (Compound 4)

The epoxide from the previous stage (111 g of 53% GC purity, 62.0 g, 210mmol, 1 eq) was dissolved in ethanol (1.2 L) for 1 h. The red coloredmixture was poured into 2 L Parr reactor and a solution of 10% Pd/C(14.6 g, dry) in ethanol (50 mL) was added. The mixture was reacted withhydrogen (4 bar) at 30° C. for 10 hr. Pd/C was filtered through a Celiteand the filtrate was concentrated in the rotavapor to give 108 g red oil(65% area product by GC). The product was added to 200 g silica gel,0.5% triethylamine in dichloromethane were added and the mixture wasconcentrated and loaded on a column with 620 g silica gel. Thepurification was done with 0.5% triethylamine in dichloromethane to give28 g hard residue (97.0% area by GC). The residue was heated to refluxin 34 mL dichloromethane until complete dissolution to give clear redsolution which was cooled slowly with parallel removal of some solventby nitrogen flow over the solvent. The precipitation was filtered andwashed with dichloromethane (5 mL) to give 20 g white solid, HPLC: 99.0%area, 1H-NMR assay: 99.4%.

NMR Identity Analysis of Compound 4

The following data in Tables 8 and 9 was determined using a sample of54.06 mg Compound 4, a solvent of 0.55 ml DMSO-D6, 99.9 atom % D, andthe instrument was a Bruker Avance III 400 MHz.

TABLE 8 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 7.85 1 s H5 H1^(b), H2^(b),H3^(b) C1, C3, C8 7.75 1 d, J = 7.9 Hz H1 H2 H3^(b), H5^(b) C5, C3,C2^(b) 7.65 1 d, J = 7.7 Hz H3 H2, H1^(b), H5^(b) C1, C5, C8 7.55 1 t, J= 7.6 Hz H2 H1, H3, H5^(b) C4, C6 4.15 1 d, J = 7.5 Hz H17 H13 C12^(b),C13 3.78 1 d, J = 6.6 Hz H13 H12^(b), H17 C9^(b) 3.18 3 s H18 — C62.92-2.97 2 m H10, H12 H9, H10, H12 C8, C10, C13^(b) 2.76 1 dt, J = 13.0and 3.3 Hz H8 H9 C3^(b), C4, C5^(b) 2.19-2.32 3 m H14, H9 H9, H10, H15C10, C12, C15, C16 2.16 1 d, J = 11.55 Hz H12 H12 C10, C14 2.00 1 t, J =11.2 Hz H10 H9, H10 C8^(b), C12 1.54 1 d, J = 12.3 Hz H9 H9, H10 C13^(b)1.46 2 sextet, J = 7.3 Hz H15 H14, H16 C14, C16 0.88 3 t, J = 7.3 Hz H16H15 C14, C15 ^(a)The assignment is based on the coupling pattern of thesignals, coupling constants and chemical shifts. ^(b)Weak signal.^(c)Spectra is calibrated by the solvent residual peak (2.5 ppm).

TABLE 9 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 145.6 C4140.4 C6 133.3 C3 128.8 C2 126.3 C5 124.4 C1 67.8 C13 60.1 C12 59.8 C1453.3 C10 45.6 C8 43.6 C18 25.2 C9 19.3 C15 11.9 C16 ^(a)The assignmentis based on the chemical shifts and 1H-13C couplings extracted from HSQCand HMBC experiments. ^(b)Spectra is calibrated by a solvent peak (39.54ppm)

Example 5—Preparation of Compound 5(4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide)

Pridopidine (50.0 g, 178 mmol, 1 eq) was dissolved in methanol (250 mL)and 33% hydrogen peroxide (20 mL, 213 mmol, 1.2 eq). The reactionmixture was heated and kept at 40° C. for 20 h. The reaction mixture wasthen concentrated in a rotavapor to give 71 g light-yellow oil. Water(400 mL) was added and the suspension was extracted with isopropylacetate (150 mL) which after separation contains unreacted pridopidinewhile water phase contains 91% area of Compound 5 (HPLC). The productwas then washed with dichloromethane (400 mL) after adjusting the waterphase pH to 9 by sodium hydroxide, After phase separation the waterphase was washed again with dichloromethane (200 mL) to give 100% areaof Compound 5 in the water phase (HPLC). The product was then extractedfrom the water phase into butanol (1×400 mL, 3×200 ml) and the butanolphases were combined and concentrated in a rotavapor to give 80 g yellowoil (HPLC: 100% area of Compound 5). The oil was washed with water (150mL) to remove salts and the water was extracted with butanol. Theorganic phases were combined and concentrated in a rotavapor to give 43g of white solid which was suspended in MTBE for 1 hr, filtered anddried to give 33 g solid that was melted when standing on air. Afterhigh vacuum drying (2 mbar, 60° C., 2.5 h) 32.23 g pure Compound 5 wereobtained (HPLC: 99.5% area, 1H-NMR assay: 97.4%).

NMR Identity Analysis of Compound 5

The following data in Tables 10 and 11 was determined using a sample of63.06 mg Compound 5, a solvent of 1.2 ml DMSO-D6, 99.9 atom % D, and theinstrument was a Bruker Avance III 400 MHz.

TABLE 10 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 7.81 1 bs H5 — C1, C3, C87.78-7.80 1 m H1 H2 C3, C5 7.63-7.66 1 m H3 H2 C1, C4^(b), C5, C87.59-7.63 1 m H2 H1, H3 C1^(b), C4, C6 3.27 2 t, J = 11.2 Hz H10, H12H9, H10, H12, C8, C9, C13 H13 3.23 3 s H18 — C1^(b), C6 3.07-3.11 2 mH14 H15 C10, C12, C15, C16 3.02 2 d, d = 13.1 Hz H10, H12 H9, H10, H12,C8, C9^(b), C13^(b) H13 2.81 1 t, J = 12.7 Hz H8 H9, H13 C3b, C4, C5b,C9, C13, C10, C12 2.39-2.50 2 m H9, H13 H8, H9, H10, C4, C8, C10, H12,H13 C12, C9, C13 1.79-1.89 2 m H15 H14, H16 C14, C16 1.64 2 d, J = 12.8Hz H9, H13 H8^(b), H9, C4b, C8b, C10b, H10^(b), H12^(b), C12b H13 0.90 3t, J = 7.5 Hz H16 H15 C14, C15 ^(a)The assignment is based on thecoupling pattern of the signals, coupling constants and chemical shifts.^(b)Weak signal. ^(c)Spectra is calibrated by the solvent residual peak(2.5 ppm).

TABLE 11 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 146.9 C4141.0 C6 132.1 C3 129.6 C2 125.0 C1 124.9 C5 72.4 C14 63.4 C10, C12 43.5C18 39.4 C8 27.3 C9, C13 15.1 C15 11.3 C16 ^(a)The assignment is basedon the chemical shifts and 1H-13C couplings extracted from HSQC and HMBCexperiments. ^(b)Spectra is calibrated by a solvent peak (39.54 ppm)

Example 6—Preparation of Compound 6(1-(2-methylpentyl)-4-(3-(methylsulfonyl)phenyl)piperidine)

Into a 1 L autoclave was added KI (28.4 g, 171 mmol 1 eq) and potassiumcarbonate (47.4 g, 343 mmol, 2 eq).4-(3-(methylsulfonyl)phenyl)piperidine (41 g, 171 mmol, 1 eq) wasdissolved in acetonitrile (420 mL) and the mixture was added into theautoclave followed by 1-chloro-2-methylpentane (25.8 mL, 188 mmol, 1.1eq). The autoclave was closed and the reaction mixture was heated undernitrogen atmosphere to 120° C. for 30 hr. The reaction mixture wascooled down and filtered. The cake was washed with acetonitrile and thefiltrate was concentrated in vacuum to give 70 g crude product with thefollowing HPLC areas: 60% of Compound 6, 1% of4-(3-(methylsulfonyl)phenyl)piperidine and 10% of a by-product. Thecrude product was dissolved in toluene (350 ml) and about 20 g solidmaterial was filtered. The toluene phase was washed with water (200 mL)and concentrated in a rotavapor to give 35.5 g (73% area of product byHPLC). The residue was then dissolved in ethyl acetate (180 mL) andcooled on ice bath. Into the reaction mixture was then added 33 mL of18% HCl solution in ethyl acetate in 1 hr and the mixture was stirredfor an additional 1 h. The precipitate that was formed was thenfiltered, washed with ethyl acetate and dried to give 36.3 g white solid(HPLC: 94% area. The product was recrystallized by dissolving inmethanol (290 mL), heating to 70° C., adding ethyl acetate (400 mL) andcooling to room temperature. The precipitate was filtered, washed withethyl acetate (60 mL) and dried in vacuum at 50° C. to give 28.3 gCompound 6 (HPLC: 99.5% area. 1H-NMR assay: 99.6%).

NMR Identity Analysis of Compound 6

The following data in Tables 12 and 13 was determined using a sample of33.93 mg Compound 6, a solvent of 8 ml DMSO-D6, 99.9 atom % D, and theinstrument was a Bruker Avance III 400 MHz. Two conformers (ca 10:1) atroom temperature are observed. Due to the overlap of proton signals ofthe major and minor conformers and relatively weak signal of the minorisomer in 2 D spectra only some of the peaks of minor isomer on 1Hspectra and corresponding 1H-1H COSY cross peaks are given. Due to thelow solubility of the material in D6-DMSO some of the expected HMBCsignals are masked by background noise.

TABLE 12 Assignment of ¹H NMR^(a,c) ¹H Shift COSY cross HMBC cross (ppm)Integral Multiplicity Assignment peaks peaks 9.88 1 bs NH H10, H12, —H14 7.79-7.84 2 m H1, H5 H2, H3 C1, C3, C5, C8 7.62-7.66 2 m H2, H3 H1,H5 C1, C4, C5, C6, C8^(b) 3.53-3.63 2 m H10, H12 H10, H12 — 3.23 3 s H18— C5^(b), C6 2.87-3.11 5 m H8, H10, H12, H9, H10, H12, C9, C12^(b), C13,C15, H14 H13, H15 C16, C19^(b) 2.17-2.34 2 m H9, H13 H8, H9, H10, — H12,H13 1.94-2.02 3 m H9, H13, H15 H8, H9, H10, — H12, H14, H19, H161.22-1.45 3 m H19, H20 H15, H19, C20 H20, H21 1.10-1.21 1 m H19 H15, H20C16, C20, C21 1.02 3 d, J = 6.7 Hz H16 H15 C14, C15, C19 0.90 3 t, J =6.S Hz H21 H20 C19, C20 Minor isomer 10.14  1 bs NH H10, H12 — 7.88 1 sH5 — — 7.75 1 d, J = S.5 Hz H1 H2 — 3.24-3.31 4 m H10, H12 H9, H13 —1.86-1.84 3 m H9, H13, H15 H10, H12, — H16 ^(a)The assignment is basedon the coupling pattern or the signals, coupling constants and chemicalshifts. ^(b)Weak signal. ^(c)Spectra is calibrated by the solventresidual peak (2.5 ppm).

TABLE 13 Assignment of ¹³C NMR^(a,b) ¹³C Shift (ppm) Assignment 145.9 C4141.1 C6 131.9 C3 129.8 C2 125.3 C1 124.9 C5 62.5 C14 53.1 C10 51.8 C1243.5 C18 38.5 C8 36.4 C19 29.20 and 29.24 C9, C13 27.5 C15 19.1 C20 18.0C16 14.0 C21 ^(a)The assignment is based on the chemical shifts and1H-13C couplings extracted from HSQC and HMBC experiments. ^(b)Spectrais calibrated by a solvent peak (39.54 ppm)

Example 7—Preparation of Compound 7(4-(3-(methylsulfinyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine)

Sulfuric acid (42.23 g, 0.431 mol, leg) was added to a mixture of4-hydroxy-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-1-ium chloride(130 g, 0.431 mo, 1 eq) and toluene (650 mL) at room temperature. Theresulting two-phase solution was refluxed for 1 hour and HPLC showedthat the product reached 95% area. The reaction mixture was cooled downto 20° C. and the toluene phase was decanted to give viscous residuethat was diluted with water (600 mL) and neutralized with 2N NaOH topH-4.2. Hydrogen peroxide (50%, 32.21 g, 0.474 mol, 1.1 eq) was addeddropwise to the water phase and the mixture was stirred at 60° C. for 1h after which the product reached 96% area (HPLC).

Toluene (600 mL) was added to the reaction mixture and made basic firstwith 25% NaOH (60 g) and finally with 10% NaOH up to pH 12. The phaseswere separated and the water phase was re-extracted with toluene (2×100mL). The combined toluene phases were washed with 5% sodium sulfite (150mL), brine (150 mL) and water (150 mL). The toluene phase was thenconcentrated under vacuum on a rotavapor to give 111.3 g oil (HPLC area:96.6%). Methanol (50 mL) was added to the residue and it was filteredand cooled down on ice batch. Dry HCl in ethyl acetate was added up topH 1-2 (120 mL) and 100 mL of ethyl ether were added to give two phasesmixture. The mixture was seeded with the product and precipitationstarted. The reaction mixture was stirred on ice bath (2-5° C.) foradditional 1 h, filtered and washed with ⅓ ethyl acetate/ether mixture(100 mL) to give 140 g of very hygroscopic light yellow solid that wasdried on a rotavapor for 2 h and stored under nitrogen in deep freeze.The dry4-(3-(methylsulfinyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine-HCl isslightly yellowish solid (94.1 g, 79% yield, HPLC (254 nm): 96.3% area,1H-NMR assay: 97.5%).

NMR Identity Analysis of Compound 7

The following data in Tables 14 and 15 was determined using a sample ofCompound 7, a solvent of CDCl₃, and the instruments were a Bruker AMX500and Avarice III 800 MHz instrument.

TABLE 14 Assignment of ¹H NMR^(a) ¹H Shift ¹H Shift COSY cross (ppm)(ppm)^(b) Integral Multiplicity Assignment peaks 2.63 2.66 2 t, 2 × 5.7to H3 H2 H3 2.51 2.55 2 m H3 H2, H5, H6 6.10 6.13 1 tt, 2 × 3.6 to H6, 2× 1.5 H5 H3, H6 to H3 3.09 3.13 2 m H6 H3, H5 2.35 2.39 2 m H7 H8 1.511.54 2 m H8 H7, H9 0.86 0.89 3 t, 2 × 7.4 to H8 H9 H8 7.60 7.49 1 dt,0.4 to H5′, 2 × 1.8 to H2′ H4′, H5′, H6′ H4′ and H6′ 7.37 7.40 1 ddd,1.4 to H6′, 1.8 to H4′ H2′, H5′, H6′ H5′, 7.6 to H2′ 7.36 7.37 1 dt, 0.4to H2′, 2 × 7.6 to H5′ H2′ H4′, H6′ H4′ and H6′ 7.41 7.44 1 ddd, 1.4 toH4′, 1.8 to H6′ H2′, H4′, H5′ H5′, 7.6 to H2′ 2.62 2.66 3 s H7′ —^(a)Spectra is calibrated by the solvent residual peak (2.5 ppm).^(b)after addition of small amount of C₆D₆

TABLE 15 Assignment of ¹³C NMR^(a,) ¹³C Shift HMBC ¹H (ppm) Assignmentcross peaks 49.89 C2 C4, 6, 7 27.68 C3 C2, 4, 5 133.67 C4 — 123.57 C5C3, 6, 1′ 52.90 C6 C2, 4, 5, 7 60.04 C7 C2, 6, 8, 9 20.02 C8 C7, 9 11.72C9 C7, 8 142.00 C1′ — 119.41 C2′ C4, 6, 3′, 4′ 145.52 C3′ — 121.51 C4′C2′ 6′ 128.97 C5′ — 127.19 C6′ C2′, 4′, 4 43.70 C7′ 3′ ^(a)Spectra iscalibrated by a solvent peak (77.0 ppm)

Example 8—Analysis of the Amounts of Compounds 1, 2, 3, 4, 5 and 6 in aSample of Pridopidine Drug Substance

Compounds 1-7 are useful to determine the purity of a pridopidinecontaining composition.

The procedure used for determination of assay and related substances inpridopidine HCl is a reverse phase HPLC method using X-bridge phenylcolumn (or equivalent) and gradient elution with UV detection at 268 nm.The mobile phase consists of a mixture of methanol and ammonium formatebuffer.

Apparatus

HPLC with gradient pump, column thermostat and UV-detector. Column:Waters, X-bridge Phenyl, 75×4.6 mm, 2.5 μm; or an equivalent column.

Analytical Instruction

Reagents and Solutions

Solvents: Methanol, HPLC grade; Water, MilliQ-water or equivalent

Reagents: Ammonium formate, purum; Ammonium hydroxide, 30% A.C.S; Formicacid, pa Ammonium formate buffer, 1.00 mM, pH 8.90-9.10: Weigh 6.3-6.4 gammonium formate accurately into a 1000 mL volumetric flask and add 2.5ml 30% ammonium hydroxide solution. Dissolve and dilute withmilliQ-water to 900 mL, Measure the pH of the solution. The pH should bebetween 8.90 and 9.10, otherwise adjust with ammonium hydroxide orformic acid. Dilute to volume and filter through a 0.45 μm HVLP-filter.

Reference substances: Control Sample 1a: (pridopidine)(see FIG. 1;Control Sample 2b (Compound 5, Compound 1, Compound 4, pridopidine,Compound 8, Compound 2, Compound 6, Compound 3)

TABLE 16 Phase Solvent Amount Mobile phase Ammonium formate buffer, 100mM, pH 9.0 100 mL A MilliQ-water 900 mL Mobile phase Ammonium formatebuffer, 100 mM, pH 9.0 100 mL B MilliQ-water 50 mL Methanol 850 mLDilution phase Methanol 150 mL MilliQ-water 850 mL

TABLE 17 Analytical conditions Flow 0.8 mL/min Gradient Time (min)Mobile phase B (%) 0 50 10 100 12 100 Equilibration time 3 min.Wavelength 268 nm (bandwidth 4 nm; reference off) 190-400 nm (forinformation in stability studies only). Injected volume 20 μL Needlewash Set wash cycles to two. Use dilution phase in washing vial.Temperature 40° C.

TABLE 18 Approximate retention times Substance Time (min) Compound 5 1.9Compound 1 2.4 Compound 4 3.5 Pridopidine 4.6 Compound 8 6.1 Compound 27.5 Compound 6 8.8 Compound 3 9.9Blank Preparation:

Use dilution phase. Duplicate vials of blank (A and B).

Reference Preparation a (Only for Related Substances)

Use Control Sample 2b. Inject as it is.

The Control Sample 2b solution is a pridopidine solution (0.44 mg/mlfree base) spiked with approximately 1% of each of the impurities:Compound 5, Compound 1, Compound 4, Compound 8, Compound 2, Compound 6and Compound 3.

Reference Preparation B (Only for Assay)

Duplicate preparation (B1 and B2).

Weigh 43-45 mg of pridopidine reference into a 50 mL volumetric flask.Add 25 dilution phase and shake or sonicate at ambient temperature untilthe reference is dissolved. Make to volume with dilution phase.Concentration: 0.9 mg/mL pridopidine. The standard solution is stablefor 48 hours when stored in daylight and in room temperature.

Reference Preparation C (Only for Related Substances)

Single preparation (C).

Dilute 1 mL of reference B1 to 100 mL with dilution phase. Dilutefurther 1 mL of this solution to 20 mL with dilution phase (sensitivitystandard, concentration corresponding to 0.05% of sample concentration).

Sample Preparation

Duplicate preparation (sample A and B).

Weigh 43-45 mg of the sample of pridopidine into a 50 mL volumetricflask. Add 25 mL dilution phase and shake or sonicate at ambienttemperature until the sample is dissolved. Make to volume with dilutionphase. Concentration: 0.9 mg/mL pridopidine. The sample solution shouldbe freshly prepared before use.

Order of Determinations

When the system is equilibrated, inject the solutions in the followingorder:

TABLE 19 Number of determinations/injections Solution Assay Relatedsubstances Blank A 3 (at least) 1 (at least) Blank B 1 1 Reference A N/A1 Reference C N/A 1 Reference B1 5 N/A Reference B2 1 N/A Sample A 1 1Sample B 1 1 . . . . . . . . . Reference B2 1 N/ACalculationSystem SuitabilityFor Related Substances:

R1) The Blank B should be free from interfering peaks at the retentiontimes of Compound 5, Compound 1, Compound 4, pridopidine, Compound 8,Compound 2, Compound 6 and Compound 3.

R2) The retention time of the pridopidine peak should be 4.6±0.5 min.

R3) Compound 5, Compound 1, Compound 4, pridopidine, Compound 8,Compound 2, Compound 6 and Compound 3 in the Control Sample 2b should bepossible to identify according to FIG. 2.

R4) The pridopidine peak in reference C should have a signal-to-noiseratio greater than or equal to 3.

R5) Calculate the number of theoretical plates (N) and the tailingfactor (T) for the pridopidine peak in reference A. Number oftheoretical plates 2: 8000 and tailing factor 0.7-1.0.

R6) Calculate the resolution between Compound 5 and Compound 1 in theControl Sample 2b, should be greater than or equal to 1.5.

R7) If the problem with split peaks Compound 1 and Compound 4 shallappear, they should be calculated as sum of each split peak.

For Assay:

A1) The Blank B should be free from interfering peak at the retentiontime for pridopidine.

A2) The retention time of the pridopidine peak should be 4.6±0.5 min.

A3) Calculate the RSD % of the five areas of reference B1. The RSDshould be ˜2.0%.

A4) Calculate the assay of each injections of reference B2. The assayshould be in the interval 99-101 w/w-% of the assay of the reference B1.

A5) Calculate the number of theoretical plates (N) and the tailingfactor (T) for the pridopidine peak in the first injection of referenceB1. Number of theoretical plates 2: 8000 and tailing factor 0.7-1.0.

A6) Calculate the deviation between the two assay determinations (SampleA and B) according to eq. 1. The deviation should be less than or equalto 2%.

$\begin{matrix}{\frac{{{{Assay}_{A} - {Assay}_{B}}} \times 100}{\left( {{Assay}_{A} + {Assay}_{B}} \right) \times 0.5} \leq {2\%}} & \left( {{eq}.\mspace{14mu} 1} \right)\end{matrix}$

The analytical method description described herein will be updated toinclude acceptance criteria for number of theoretical plates (N) and thetailing factor (T) for pridopidine peak.

Result

For Related Substances:

The content of related substances should be calculated as area-% andcorrected with relative response factors and reported as % according toeq. 2.%_(x)=area−%_(x)×RRF_(x)  (eq.2)%_(x) percent content of an impurity ‘x’area-%_(x) area-% of an impurity ‘x’ calculated from the chromatogramRRF_(x) Relative Response Factor of an impurity ‘x’

Use following response factors:

TABLE 20 Name Relative response factor Compound 8 0.2 Compound 2 0.7

Remaining related substances will be correct for RRF 1.

For assay:

Calculate the assay of pridopidine in w/w-% using the external standardmethodology (see below). Use the mean response factor obtained from thefive injections of reference B1 for the calculation.

$\begin{matrix}{f_{x} = \frac{c_{xR}}{A_{xR}}} & \left( {{eq}.\mspace{14mu} 3} \right) \\{\frac{A_{xS} \times f_{x} \times 100}{c_{xS}} = {{pridopidine}\mspace{14mu}\left( {{w\text{/}w} - \%} \right)}} & \left( {{eq}.\mspace{14mu} 4} \right)\end{matrix}$f_(x) mean response factor of pridopidine from reference solution B1c_(x)R concentration of pridopidine in reference solution (mg/ml)c_(x)S concentration of sample solution (mg/mL)A_(x)R area of pridopidine in each injection of reference solution B1A_(x)S area of pridopidine in sample chromatogram

TABLE 21 Analytical Methods for Determination of Impurities in the DrugSubstance Quanti- tation Quanti- Detec- Limit tation tion Example Method(wegith- limit limit Parameter Number Type %) (area-%) (area-%) Compound1 Example 8 RP-HPLC 0.04 0.04 0.01 Compound 2 Example 8 RP-HPLC 0.030.05 0.01 Compound 3 Example 8 RP-HPLC 0.05 0.05 0.03 Compound 4 Example8 RP-HPLC 0.04 0.04 0.01 Compound 5 Example 8 RP-HPLC 0.04 0.04 0.01Compound 6 Example 8 RP-HPLC 0.04 0.04 0.01

During course of the validation the response factors for Compound 5,Compound 1, Compound 4, Compound 8, Compound 2, Compound 6 and Compound3 has been evaluated and compared to the response factor of pridopidine.The relative response factor of the impurities are presented in Table22:

TABLE 22 Relative Response Factors Relative Response Factor Name (αpridopidine/α Compound 5 0.91 Compound 1 1.01 Compound 4 1.02 Compound 80.16 Compound 2 0.65 Compound 6 1.05 Compound 3 0.99

Example 9—Specification of Pridopidine Hydrochloride Drug Substance

TABLE 23 Ret. time Resolution Name (min) (tangent method) Compound 51.99 N/A Compound 1 2.42 3.3 Compound 4 3.58 6.6 pridopidine 4.68 4.9Compound 8 6.09 7.5 Compound 2 7.36 11.2 Compound 6 8.69 11.8 Compound 39.92 10.1

Pridopidine HCl is a white to almost white powder. The specifications ofpridopidine HCl are as follows:

TABLE 24 Specification of Pridopidine Hydrochloride Drug SubstanceAcceptance Test Criteria Method Description White to almost Visualinspection white powder Absence of lumps Pass Visual and touchingIdentification IR Conforms to reference IR IR spectrum X-raydiffractogram Conforms to reference XRPD X-ray diffractogram ChloridePositive Ph. Eur. Assay, HPLC, % w/w 98.0-102.0 HPLC Related substances,HPLC, area % Compound 5 ≤0.15 HPLC Compound 1 ≤0.15 HPLC Compound 4≤0.15 HPLC Compound 8 ≤0.15 HPLC Compound 3 ≤0.15 HPLC Compound 2 ≤0.15HPLC Compound 6 ≤0.15 HPLC Unknown impurities, each ≤0.10 HPLCImpurities in total ≤0.50 HPLC

Example 10—Accelerated and Long Term Stability in Pridopidine HCl DrugProduct

Batches 1, 2 and 3 were manufactured according to cGMP and in scale asthe expected commercial scale. Batches 4 and 5 were manufacturedaccording to the current route of synthesis.

The stability program for each batch is detailed below in Table 25.

TABLE 25 Pridopidine HCl Stability Testing Program Batch 1 2 3 4 5 Batch99.7 97.2 96.6 14.9 105.4 size (kg) Stability study Storage 25° C./60%RH: 0, 3, 6, 9, 25° C./60% RH: 0, 3, 6, 9, conditions 12, 18, 24, 36, 48and 12, 18, 24, 36, 48 and and testing 60 months 60 months intervals 30°C./65% RH: 0, 3, 6, 9 30° C./65% RH: 0, 3, 6, 9 and 12 months and 12months 40° C./75% RH: 0, 3 40° C./75% RH: 0, 3 and 6 months and 6 monthsTest Appearance, Appearance, parameters Identification, Identification,Crystal form, Assay, Crystal form, Assay, Impurities, Water Impurities,Water content, Microbial limit content, Microbial limit

Stability data for batches 1, 2, 3, 4 and 5 can be found in Tables26-37:

TABLE 26 Stability Data of Pridopidine HCl Batch 1 Stored at 25° C./60%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12 1824 36 48 Appearance Color and Form White White White White White WhiteWhite White White powder powder powder powder powder powder powderpowder powder Identification Complies with ref Conforms ConformsConforms Conforms Conforms Conforms Conforms Conforms Conforms (by IR)spectrum Crystal Form Complies with ref Conforms Conforms ConformsConforms Conforms Conforms Not Not Not (by X-Ray) diffractogramscheduled scheduled scheduled Assay (by HPLC) 98.0-102.0 99.9 99.7 100.2100.2 99.6 100.0 100.4 99.8 99.7 [% w/w] Impurities (by HPLC) [area %]Compound 1 ≤0.15 0.05 0.05 0.05 0.05 0.05 <0.05 <0.05 <0.05 <0.05Compound 4 ≤0.15 0.09 0.09 0.09 0.09 0.09 0.08 0.08 0.09 0.08 Each(Compound 8, ≤0.15 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05Compound 3, Compound 2, Compound 6 and Compound 5) Unknown Impurities≤0.10 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 Each Total≤0.50 0.14 0.15 0.14 0.14 0.14 0.08 0.08 0.09 0.08 Water Content (by KF)Run and record 0.03 0.03 0.02 0.01 0.02 <0.05 <0.05 0.06 <0.05 [% w/w)Microbiological Purity [cfu/g] TAMC ≤1000 <10 Not Not Not <10 Not NotNot Not scheduled scheduled scheduled scheduled scheduled scheduledscheduled TYMC ≤10 <10 Not Not Not <10 Not Not Not Not scheduledscheduled scheduled scheduled scheduled scheduled scheduled E. ColiAbsent — — — — — — — — —

TABLE 27 Stability Data of Pridopidine HCl Batch 1 Stored at 40° C./75%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6Appearance Color and White White White Form powder powder powderIdentification (by Complies with Conforms Conforms Conforms IR) refspectrum Crystal Form (by Complies with Conforms Conforms ConformsX-Ray) ref diffractogram Assay (by HPLC) 98.0-102.0 99.9 99.7 100.1 [%w/w] Impurities (by HPLC) [area %] Compound 1 ≤0.15 0.05 0.05 0.05Compound 4 ≤0.15 0.09 0.09 0.09 Each (Compound 8, ≤0.15 <0.05 <0.05<0.05 Compound 3, Compound 2, Compound 6 and Compound 5 UnknownImpurities ≤0.10 <0.05 <0.05 <0.05 Each Total ≤0.50 0.14 0.14 0.14 WaterContent (by Run and record <0.1 <0.1 <0.1 KF) [% w/w) MicrobiologicalPurity [cfu/g] TAMC ≤1000 <10 Not Not scheduled scheduled TYMC ≤10 <10Not Not scheduled scheduled E. Coli Absent — — —

TABLE 28 Stability Data of Pridopidine HCl Batch 2 Stored at 25° C./60%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12 1824 36 48 Appearance Color and Form White White White White White WhiteWhite White White powder powder powder powder powder powder powderpowder powder Identification Complies with ref Conforms ConformsConforms Conforms Conforms Conforms Conforms Conforms Conforms (by IR)spectrum Crystal Form Complies with ref Conforms Conforms ConformsConforms Conforms Conforms Not Not Not (by X-Ray) diffractogramscheduled scheduled scheduled Assay (by HPLC) 98.0-102.0 100.1 99.9100.4 100.3 100.2 100.1 100.4 99.7 100.5 [% w/w] Impurities (by HPLC)[area %] Compound 4 ≤0.15 0.05 0.05 0.05 0.05 0.05 <0.05 0.05 <0.05<0.05 Each (Compound 1, ≤0.15 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 <0.05 Compound 8, Compound 3, Compound 2, Compound 6 and Compound5) Unknown Impurities ≤0.10 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 <0.05 Each Total ≤0.50 0.05 0.05 0.05 0.05 0.05 <0.05 0.05 <0.05<0.05 Water Content (by KF) Run and record 0.03 0.02 0.01 0.01 0.02<0.05 <0.05 <0.05 <0.05 [% w/w) Microbiological Purity [cfu/g] TAMC≤1000 <10 Not Not Not <10 Not Not Not Not scheduled scheduled scheduledscheduled scheduled scheduled scheduled TYMC ≤10 <10 Not Not Not <10 NotNot Not Not scheduled scheduled scheduled scheduled scheduled scheduledscheduled E. Coli Absent — — — — — — — — —

TABLE 29 Stability Data of Pridopidine HCl Batch 2 Stored at 40° C./75%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6Appearance Color and White White While Form powder powder powderIdentification (by Complies with Conforms Conforms Conforms IR) refspectrum Crystal Form (by Complies with Conforms Conforms ConformsX-Ray) ref diffractogram Assay (by HPLC) 98.0-102.0 100.1 99.6 100.6 [%w/w] Impurities (by HPLC) [area %] Compound 4 ≤0.15 0.05 0.05 0.05 Each(Compound 1, ≤0.15 <0.05 <0.05 <0.05 Compound 8, Compound 3, Compound 2,Compound 6 and Compound 5) Unknown Impurities ≤0.10 Each Total ≤0.500.05 0.05 0.05 Water Content (by Run and record <0.1 <0.1 <0.1 KF) [%w/w) Microbiological Purity [cfu/g] TAMC ≤1000 <10 Not Not scheduledscheduled TYMC ≤10 <10 Not Not scheduled scheduled E. Coli Absent — — —

TABLE 30 Stability Data of Pridopidine HCl Batch 3 Stored at 25° C./60%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12 1824 36 48 Appearance Color and Form White White White White White WhiteWhite White White powder powder powder powder powder powder powderpowder powder Identification Complies with ref Conforms ConformsConforms Conforms Conforms Conforms Conforms Conforms Conforms (by IR)spectrum Crystal Form Complies with ref Conforms Conforms ConformsConforms Conforms Conforms Not Not Not (by X-Ray) diffractogramscheduled scheduled scheduled Assay (by HPLC) 98.0-102.0 100.5 99.8100.4 100.6 100.0 100.1 100.5 100.2 100.5 [% w/w] Impurities (by HPLC)[area %] Compound 4 ≤0.15 0.06 0.06 0.06 0.06 0.06 0.06 0.05 0.05 0.05Each (Compound 1, ≤0.15 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 Compound 8, Compound 3, Compound 2, Compound 6 and Compound 5)Unknown Impurities ≤0.10 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 Each Total ≤0.50 0.06 0.06 0.06 0.06 0.06 0.06 0.05 0.05 0.05Water Content (by KF) Run and record 0.03 0.03 0.01 0.01 0.01 <0.05<0.05 <0.05 <0.05 [% w/w) Microbiological Purity [cfu/g] TAMC ≤1000 <10Not Not Not <10 Not Not Not Not scheduled scheduled scheduled scheduledscheduled scheduled scheduled TYMC ≤10 <10 Not Not Not <10 Not Not NotNot scheduled scheduled scheduled scheduled scheduled scheduledscheduled E. Coli Absent — — — — — — — — —

TABLE 31 Stability Data of Pridopidine HCl Batch 3 Stored at 40° C./75%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6Appearance Color and White White White Form powder powder powderIdentification (by Complies with Conforms Conforms Conforms IR) refspectrum Crystal Form (by Complies with Conforms Conforms ConformsX-Ray) ref diffractograrn Assay (by HPLC) 98.0-102.0 100.5 99.7 100.5 [%w/w] Impurities (by HPLC) [area %] Compound 4 ≤0.15 0.06 0.06 0.06 Each(Compound 1, ≤0.15 <0.05 <0.05 <0.05 Compound 8, Compound 3, Compound 2,Compound 6 and Compound 5) Unknown Impurities ≤0.10 <0.05 <0.05 <0.05Each Total ≤0.50 0.06 0.06 0.06 Water Content (by Run and record <0.1<0.1 <0.1 KF) [% w/w) Microbiological Purity [cfu/g] TAMC ≤1000 <10 NotNot scheduled scheduled TYMC ≤10 <10 Not Not scheduled scheduled E. ColiAbsent — — —

TABLE 32 Stability Data of Pridopidine HCl Batch 4 Stored at 25° C./60%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12 1824 36 Appearance Color and Form White White White White White WhiteWhite White powder powder powder powder powder powder powder powderIdentification Complies with ref Conforms Conforms Conforms ConformsConforms Conforms Conforms Conforms (by IR) spectrum Crystal FormComplies with ref Conforms Not Not Not Not Not Not Not (by X-Ray)diffractogram scheduled scheduled scheduled scheduled scheduledscheduled scheduled Assay (by HPLC) 98.0-102.0 100.4 98.6 99.8 99.7 99.599.9 99.8 100.1 [% w/w] Impurities (by HPLC) [area %] Compound 4 ≤0.150.06 0.06 0.07 0.06 0.07 0.06 0.06 0.06 Compound 3 ≤0.15 0.06 <0.05 0.060.08 0.06 0.07 0.06 0.05 Compound 8 ≤0.15 <0.01 <0.01 <0.01 <0.01 <0.01<0.01 <0.01 <0.01 Each (Compound 1, ≤0.10 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 <0.05 <0.05 Compound 2, Compound 6, Compound 5 and UnknownImpurities Each) Total ≤0.50 0.12 0.06 0.13 0.14 0.13 0.14 0.13 0.11Water Content Run and record 0.06 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 (by KF) [% w/w) Microbiological Purity [cfu/g] TAMC ≤1000 <10 NotNot Not Not Not Not Not scheduled scheduled scheduled scheduledscheduled scheduled scheduled TYMC ≤10 <10 Not Not Not Not Not Not Notscheduled scheduled scheduled scheduled scheduled scheduled scheduled E.Coli Absent Not Not Not Not Not Not Not Not detectable scheduledscheduled scheduled scheduled scheduled scheduled scheduled

TABLE 33 Stability Data of Pridopidine HCl Batch 4 Stored at 30°C./65%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 912 Appearance Color and Form White powder White powder White powderWhite powder White powder Identification (by IR) Complies with refConforms Conforms Conforms Conforms Conforms spectrum Crystal Form (byX- Complies with ref Conforms Not scheduled Not scheduled Not scheduledConforms Ray) diffractogram Assay (by HPLC) [% 98.0-102.0 100.4 99.099.5 100.0 99.6 w/w] Impurities (by HPLC) [area %] Compound 4 ≤0.15 0.060.07 0.07 0.06 0.06 Compound 3 ≤0.15 0.06 <0.05 0.07 0.07 0.06 Compound8 ≤0.15 <0.01 <0.01 <0.01 <0.01 <0.01 Each (Compound 1, ≤0.15 <0.05<0.05 <0.05 <0.05 <0.05 Compound 2, Compound 6, Compound 5 and UnknownImpurities Each) Total ≤0.50 0.12 0.07 0.13 0.13 0.12 Water Content (byKF) Run and record <0.1 <0.1 <0.1 <0.1 <0.1 [% w/w) MicrobiologicalPurity [cfu/g] TAMC ≤1000 <10 Not scheduled Not scheduled Not scheduled<10 TYMC ≤10 <10 Not scheduled Not scheduled Not scheduled <10 E. ColiAbsent Not detectable Not scheduled Not scheduled Not scheduled Notdetectable

TABLE 34 Stability Data of Pridopidine HCl Batch 4 Stored at 40° C./75%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6Appearance Color and White White White Form powder powder powderIdentification (by Complies with Conforms Conforms Conforms IR) refspectrum Crystal Form (by Complies with Conforms Not Conforms X-Ray) refscheduled diffractogram Assay (by HPLC) 98.0-102.0 100.4 99.5 99.7 [%w/w] Impurities (by HPLC) [area %] Compound 4 ≤0.15 0.06 0.07 0.07Compound 3 ≤0.15 0.06 <0.05 0.07 Compound 8 ≤0.15 <0.01 <0.01 <0.01 Each(Compound 1, ≤0.15 <0.05 <0.05 <0.05 Compound 2, Compound 6, Compound 5and Unknown Impurities Each) Total ≤0.50 0.12 0.07 0.13 Water Content(by Run and record 0.06 <0.05 <0.05 KF) [% w/w) Microbiological Purity[cfu/g] TAMC ≤1000 <10 Not <10 scheduled TYMC ≤10 <10 Not <10 scheduledE. Coli Absent Not Not Not detectable scheduled detectable

TABLE 35 Stability Data of Pridopidine HCl Batch 5 Stored at 25° C./60%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12 1824 Appearance Color and Form White White White White White White Whitepowder powder powder powder powder powder powder Identification (by IR)Complies with Conforms Conforms Conforms Conforms Conforms ConformsConforms ref spectrum Crystal Form (by X-Ray) Complies with ref ConformsNot Not Not Not Not Not diffractogram scheduled scheduled scheduledscheduled scheduled scheduled Assay (by HPLC) [% 98.0-102.0 99.8 100.099.9 99.9 99.7 100.1 100.1 w/w] Impurities (by HPLC) [area %] Compound 3≤0.15 0.10 0.09 0.07 0.09 0.11 0.11 0.07 Compound 8 ≤0.15 <0.01 <0.01<0.01 <0.01 <0.01 <0.01 <0.01 Each (Compound 1, ≤0.15 <0.05 <0.05 <0.05<0.05 <0.05 <0.05 <0.05 Compound 5, Compound 4, Compound 2, Compound 6and Unknown Impurities Each) Total ≤0.50 0.10 0.09 0.07 0.09 0.11 0.110.07 Water Content (by KF) Run and record <0.05 <0.05 <0.05 <0.05 <0.05<0.05 <0.05 [% w/w) Microbiological Purity [cfu/g] TAMC ≤1000 Not NotNot Not Not Not Not scheduled scheduled scheduled scheduled scheduledscheduled scheduled TYMC ≤10 Not Not Not Not Not Not Not scheduledscheduled scheduled scheduled scheduled scheduled scheduled E. ColiAbsent Not Not Not Not Not Not Not scheduled scheduled scheduledscheduled scheduled scheduled scheduled

TABLE 36 Stability Data of Pridopidine HCl Batch 5 Stored at 30° C./65%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6 9 12Appearance Color and Form White powder White powder White powder Whitepowder White powder Identification (by IR) Complies with ref ConformsConforms Conforms Conforms Conforms spectrum Crystal Form (by X-Complies with ref Conforms Not scheduled Not scheduled Not scheduledConforms Ray) diffractogram Assay (by HPLC) [% 98.0-102.0 99.8 99.8 99.899.8 99.7 w/w] Impurities (by HPLC) [area %] Compound 8 ≤0.15 <0.01<0.01 <0.01 <0.01 <0.01 Compound 3 ≤0.15 0.10 0.10 0.07 0.10 0.10 Each(Compound 5, ≤0.15 <0.05 <0.05 <0.05 <0.05 <0.05 Compound 4, Compound 1,Compound 2, Compound 6 and Unknown Impurities Each) Total ≤0.50 0.100.10 0.07 0.10 0.10 Water Content (by KF) Run and record <0.05 <0.05<0.05 <0.05 <0.05 [% w/w) Microbiological Purity [cfu/g] TAMC ≤1000 Notscheduled Not scheduled Not scheduled Not scheduled <10 TYMC ≤10 Notscheduled Not scheduled Not scheduled Not scheduled <10 E. Coli AbsentNot scheduled Not scheduled Not scheduled Not scheduled Not detectable

TABLE 37 Stability Data of Pridopidine HCl Batch 5 Stored at 40° C./75%RH Acceptance Storage Period (Months) Parameters Criteria 0 3 6Appearance Color and White White White Form powder powder powderIdentification (by Complies with Conforms Conforms Conforms IR) refspectrum Crystal Form (by Complies with Conforms Not Conforms X-Ray) refscheduled diffractogram Assay (by HPLC) 98.0-102.0 99.8 99.9 99.5 [%w/w] Impurities (by HPLC) [area %] Compound 8 ≤0.15 <0.01 <0.01 <0.01Compound 3 ≤0.15 0.10 0.10 0.06 Each (Compound 5, ≤0.15 <0.05 <0.05<0.05 Compound 4, Compound 1, Compound 2, Compound 6 and UnknownImpurities Each) Total ≤0.50 0.10 0.10 0.06 Water Content (by Run andrecord <0.05 <0.05 <0.05 KF) [% w/w) Microbiological Purity [cfu/g] TAMC≤1000 Not Not <10 scheduled scheduled TYMC ≤0 Not Not <10 scheduledscheduled E. Coli Absent Not Not Not scheduled scheduled detectableSummary of the Results in Tables 26-37 and Conclusions:Appearance:

No significant change is observed in color or form when stored at 40°C./75% RH for up to 6 months, at 30° C./65% RH for up to 12 months or at25° C./60% RH for up to 48 months.

Crystal Form:

No change in polymorphic form is observed when pridopidine HCl is storedat 40° C./75% RH for up to 6 months and at 30° C./65% RH for up to 12months. X-Ray diffractograms recorded after 18 months at 25° C./60% RHshowed no change. X-Ray analyses will be performed again at the end ofthe long term stability program (60 months).

Assay:

When pridopidine HCl is stored at 40° C./75% RH for up to 6 months, nosignificant change in assay is observed. Similar no significant changeis observed when stored at 30° C./65% RH for up to 12 months or at 25°C./60% RH for up to 48 months.

Impurities:

No degradation of pridopidine HCl is observed when the drug substance isstored at 40° C./75% RH for up to 6 months, at 30° C./65% RH for up to12 months or at 25° C./60% RH for up to 48 months.

Water Content

No significant change regarding water content is observed whenpridopidine HCl is stored at 40° C./75% RH for up to 6 months, at 30°C./65% RH for up to 12 months or at 25° C./60% RH for up to 48 months.

Conclusion:

No evidence of relevant changes was observed for the parameters testedat any of the storage conditions. Pridopidine HCl is consideredphysically and chemically stable when stored at 40° C. and 75% RH for upto 6 months, at 30° C./65% RH for up to 12 months or at 25° C. and 60%RH for up to 48 months.

Example 11—Forced Degradation Study

A forced degradation study has been performed on pridopidine HCl drugproduct and drug substance. The studied material was subjected to acidand base hydrolysis, thermal stress both as solid and in solution,oxidation, humidity induced stress and photolysis.

The study showed that pridopidine HCl is very stable under most of thestudied conditions except for when subjected to oxidative conditions,where considerable degradation was observed. The major degradationproduct was Compound 5. There was also some degradation in the basichydrolysis study but only a minor total degradation was observed withthe largest degradation product being unidentified.

Mass balance was also investigated and found to be good for all studiedconditions.

Summary and Conclusions of Examples 10-11

The amounts of the organic impurities remained below the acceptedcriteria in all the conditions tested over all time periods as shown inExample 10. Compound 5, which is the only known potential degradationproduct (Example 11), remained low in all the tested conditions as shownin Example 10.

Example 12—Specification of Pridopidine HCl Drug Product

As detailed in example 10, no degradation products have been detected inthe pridopidine HCl in any storage conditions. In addition, noadditional impurities are created during the formation of the drugproduct. Therefore, the same amounts of the organic impurities Compound1, Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6 whichare controlled in the drug substance remain in the drug product, and theaccepted criteria relating to the organic impurities Compound 1,Compound 2, Compound 3, Compound 4, Compound 5, and Compound 6 asdetailed in Table 22 are relevant to the drug product.

Example 13—Batch Analysis of Pridopidine HCl Drug Substance

A number of batches of Pridopidine HCl drug substance were manufacturedat various manufacturing facilities and subsequently analyzed. Allbatches contained the known identified impurities Compound 5, Compound1, Compound 4. Compound 8 Compound 6 and Compound 3 in levels below thequalification limit of 0.15%.

TABLE 38 Analysis of the content of each of the impurities Compound 5,Compound 1, Compound 4, Compound 8 Compound 6 and Compound 3 availablein the API batches used for tox studies Impurity/Batch No. Z Y XCompound 5 NP NP <0.05 Compound 1 NP NP 0.06 Compound 4 NP <0.05 0.06Compound 8 0.02 NP <0.05 Compound 6 NP <0.05 <0.05 Compound 2 NP NP<0.05 Compound 3 NP <0.05 <0.05 Largest impurity 0.15 <0.05 <0.05 NP—Notperformed

Example 14—Batch Analysis of Pridopidine HCl Drug Product

A number of batches of Pridopidine HCl drug product were manufactured atvarious manufacturing facilities and subsequently analyzed.

TABLE 39 Analysis of Pridopidine HCl Batches used for Non-Clinical andClinical Studies Related Substances by HPLC [area %] Compound CompoundBatch Number Compound 5 Compound 1 4 (Peak 1) Compound 8 3 (Peak 2)Compound 2 Acceptance ≤0.15  ≤0.15 ≤0.15 ≤0.15  ≤0.15 ≤0.15  Criteria A— — — — — — B — — — — — — C — — <0.05 — 0.06 — D — — <0.05 — <0.05 — E —— <0.05 — <0.05 — F — — <0.05 — <0.05 — 1 — — 0.09 — ND — 2 — — 0.05 —ND — 3 — — 0.05 — ND — 4 <0.05 <0.05 0.08 <0.05 0.07 <0.05 5  <0.05²<0.05 <0.05 <0.05 0.10 <0.05 G <0.05 0.06 <0.05 <0.01 0.10 <0.05 H <0.050.07 <0.05 <0.01 0.08 <0.05 I <0.05 <0.05 0.06 <0.01 0.11 <0.05 J <0.05<0.05 <0.05 <0.01 <0.05 <0.05 K <0.05 0.07 <0.05 <0.01 0.08 <0.05Related Substances by HPLC [area %] Compound Unknown Impurities BatchNumber 6 (Peak 3) Compound 9 Impurities in Total Acceptance ≤0.15 Report ≤0.10 each ≤0.50 Criteria value A — — — 0.51 B — — — 0.26 C <0.05— <0.05 0.06 D <0.05 — <0.05 <0.05 E <0.05 — 0.09¹ 0.09 F <0.05 — 0.07¹0.07 1 ND — 0.05 0.14 2 ND — ND 0.05 3 ND — ND 0.06 4 <0.05 <1 <0.050.15 5 <0.05 <1 <0.05 0.10 G <0.05 <1 <0.05 0.15 H <0.05 <1 <0.05 0.14 I<0.05 <1 <0.05 0.17 J <0.05 1 <0.05 <0.05 K <0.05 <1 <0.05 0.15 Compound9 is 4-hydroxy-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-1-iumchloride.

What is claimed is:
 1. An isolated compound having the structure:

(3R,4S)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol (hereinafter Compound 4), or a salt thereof.
 2. A composition comprising pridopidine and a compound which has the structure:

(3R,4S)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol (hereinafter Compound 4), or

4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol (hereinafter Compound 1), or a salt thereof.
 3. The composition of claim 2, wherein the composition is a pharmaceutical composition comprising an amount of pridopidine and at least one of Compound 1 and Compound 4 wherein a) Compound 1 is present in the pharmaceutical composition in an amount not more than 10 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or b) Compound 4 is present in the pharmaceutical composition in an amount not more than 10 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 4. The pharmaceutical composition of claim 3, comprising pridopidine hydrochloride salt.
 5. The pharmaceutical composition of claim 3, in an oral dosage unit form.
 6. The pharmaceutical composition of claim 5, wherein the oral dosage unit form comprises about 22.5 mg, about 45 mg, about 67.5 mg, about 90 mg, about 100 mg, about 112.5 mg, about 125 mg, about 135 mg, about 150 mg, or about 180 mg pridopidine.
 7. A process for producing a pridopidine drug product comprising obtaining a pridopidine drug substance and mixing the pridopidine drug substance with suitable excipients so as to produce the pridopidine drug product, wherein the pridopidine drug substance comprises the composition of claim 2, and wherein the pridopidine drug substance comprises: i) an amount of Compound 1 in the pridopidine drug substance that is not more than 0.15 area-% Compound 1, relative to the concentration of pridopidine, or ii) an amount of Compound 4 in the pridopidine drug substance that is not more than 0.15 area-% Compound 4, relative to the concentration of pridopidine.
 8. The process of claim 7, wherein the process further comprises subjecting a sample of the pridopidine drug substance to stability testing before the step of determining the amount of at least one of Compound 1 and Compound 4 in the pridopidine drug substance.
 9. A process for producing a pridopidine drug product for commercial sale comprising obtaining a batch of pridopidine drug product that comprises: i) an amount of 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol (hereinafter Compound 1) in the batch of pridopidine drug product that is not more than 0.15 area-% Compound 1, relative to the concentration of pridopidine, or ii) an amount of (3R,4S)-4-(3-(methysulfonyl)phenyl)-1-propylpiperidin-3-ol (hereinafter Compound 4) in the batch of pridopidine drug product that is not more than 0.15 area-% Compound 4, relative to the concentration of pridopidine, and preparing the batch of pridopidine drug product for commercial sale.
 10. The process of claim 9, wherein the process further comprises determining the amount of at least one of Compound 1 and Compound 4 in the batch of pridopidine drug product.
 11. The process of claim 10, wherein the process further comprises subjecting a sample of the batch of pridopidine drug product to stability testing before determining the amount of at least one of Compound 1 and Compound 4 in the sample of the batch of pridopidine drug product.
 12. A process of distributing a pridopidine drug product comprising a pridopidine drug substance comprising, a) obtaining the pridopidine drug product wherein the pridopidine drug substance comprises the composition of claim 2, and wherein the pridopidine drug substance comprises: i) an amount of Compound 1 in the pridopidine drug substance that is not more than 0.15 area-% Compound 1, relative to the concentration of pridopidine, or ii) an amount of Compound 4 in the pridopidine drug substance that is not more than 0.15 area-% Compound 4, relative to the concentration of pridopidine; and b) distributing the pridopidine drug product comprising the pridopidine drug substance.
 13. A process of distributing a pridopidine drug product comprising, a) obtaining the pridopidine drug product that comprises the composition of claim 2, and wherein the pridopidine drug product comprises: i) an amount of Compound 1 in the pridopidine drug product that is not more than 0.15 area-% Compound 1, relative to the concentration of pridopidine, or ii) an amount of Compound 4 in the pridopidine drug product that is not more than 0.15 area-% Compound 4, relative to the concentration of pridopidine; and b) distributing the pridopidine drug product.
 14. An impurity or a salt thereof for use as a reference standard to detect trace amounts of the impurity in a pharmaceutical composition comprising pridopidine or a pharmaceutically acceptable salt thereof, wherein the impurity is selected from the group consisting of the compound of claim 1 or 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol (hereinafter Compound 1).
 15. A process for validating a batch of a pharmaceutical product containing pridopidine or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier for distribution comprising: a) determining the amount of at least one of the compound according to claim 1, or 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol (hereinafter Compound 1); and b) validating the batch for distribution only if i) the batch is determined to have not more than 0.15 area-% Compound 1, relative to the concentration of pridopidine, or ii) the batch is determined to have not more than 0.15 area-% Compound 4, relative to the concentration of pridopidine.
 16. The pharmaceutical composition of claim 3, wherein the composition comprises at least one or more of 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidone (hereinafter Compound 2), 1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane (hereinafter Compound 3), 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide (hereinafter Compound 5), 1-(2-methylpentyl)-4-(3-(methysulfonyl)phenyl)piperidine (hereinafter Compound 6), and 4-(3-(methylsulfinyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridine (hereinafter Compound 7) wherein a) Compound 1 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or b) Compound 2 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or c) Compound 3 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or d) Compound 4 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or e) Compound 5 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or f) Compound 6 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 17. The pharmaceutical composition according to claim 16, wherein a) Compound 1 is present in the pharmaceutical composition in an amount greater than 0.01 area-%, and not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or b) Compound 2 is present in the pharmaceutical composition in an amount greater than 0.01 area-%, and not more than 0.15 area-%, relative to the concentration of pridopidine, based on a determination by an HPLC method, or c) Compound 3 is present in the pharmaceutical composition in an amount greater than 0.03 area-%, and not more than 0.15 area-%, relative to the concentration of pridopidine, based on a determination by an HPLC method, or d) Compound 4 is present in the pharmaceutical composition in an amount greater than 0.01 area-%, and not more than 0.15 area-%, relative to the concentration of pridopidine, based on a determination by an HPLC method, or e) Compound 5 is present in the pharmaceutical composition in an amount greater than 0.01 area-%, and not more than 0.15 area-%, relative to the concentration of pridopidine, based on a determination by an HPLC method, or f) Compound 6 is present in the pharmaceutical composition in an amount greater than 0.01 area-% and not more than 0.15 area-%, relative to the concentration of pridopidine, based on a determination by an HPLC method.
 18. The pharmaceutical composition according to claim 17, wherein a) Compound 1 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or b) Compound 2 is present in the pharmaceutical composition in an amount less than 0.05 area %, relative to the concentration of pridopidine, based on a determination by an HPLC method, or c) Compound 3 is present in the pharmaceutical composition in an amount less than 0.05 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or d) Compound 4 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or e) Compound 5 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or f) Compound 6 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 19. The pharmaceutical composition according to claim 16, wherein a) Compound 1 is present in the pharmaceutical composition in an amount less than 0.01 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or b) Compound 2 is present in the pharmaceutical composition in an amount less than 0.01 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or c) Compound 3 is present in the pharmaceutical composition in an amount less than 0.03 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or d) Compound 4 is present in the pharmaceutical composition in an amount less than 0.01 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or e) Compound 5 is present in the pharmaceutical composition in an amount less than 0.01 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or f) Compound 6 is present in the pharmaceutical composition in an amount less than 0.01 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 20. The isolated compound of claim 1, which is Compound 4 as free base.
 21. The composition of claim 3 comprising a) pridopidine, and b) Compound 1, and c) Compound
 4. 22. The pharmaceutical composition of claim 21, wherein i) Compound 1 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or ii) Compound 4 is present in the pharmaceutical composition in an amount not more than 0.15 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 23. The pharmaceutical composition according to claim 22, wherein i) Compound 1 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method, or ii) Compound 4 is present in the pharmaceutical composition in an amount less than 0.04 area-% relative to the concentration of pridopidine, based on a determination by an HPLC method.
 24. The composition of claim 2, wherein the ratio of the weight of the compound relative to the weight of the pridopidine in the composition is from 99:1 to 1:99.
 25. The process of claim 9 wherein the batch of pridopidine drug product comprises: i) an amount of 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidone (hereinafter Compound 2) in the batch of pridopidine drug product that is not more than 0.15 area-% Compound 2, relative to the concentration of pridopidine, or ii) an amount of 1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane (hereinafter Compound 3) in the batch of pridopidine drug product that is not more than 0.15 area-% Compound 3, relative to the concentration of pridopidine, or iii) an amount of 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide (hereinafter Compound 5) in the batch of pridopidine drug product that is not more than 0.15 area-% Compound 5, relative to the concentration of pridopidine, or iv) an amount of Compound 6 in the batch of pridopidine drug product that is not more than 0.15 area-% 1-(2-methylpentyl)-4-(3-(methysulfonyl)phenyl)piperidine (hereinafter Compound 6), relative to the concentration of pridopidine.
 26. The process of claim 12, wherein the pridopidine drug substance comprises one or more of 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidone (hereinafter Compound 2), 1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane (hereinafter Compound 3), 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide (hereinafter Compound 5), and 1-(2-methylpentyl)-4-(3-(methysulfonyl)phenyl)piperidine (hereinafter Compound 6) and wherein the pridopidine drug substance comprises: i) an amount of Compound 2 in the pridopidine drug substance that is not more than 0.15 area-% Compound 2, relative to the concentration of pridopidine, or ii) an amount of Compound 3 in the pridopidine drug substance that is not more than 0.15 area-% Compound 3, relative to the concentration of pridopidine, or iii) an amount of Compound 5 in the pridopidine drug substance that is not more than 0.15 area-% Compound 5, relative to the concentration of pridopidine, or iv) an amount of Compound 6 in the pridopidine drug substance that is not more than 0.15 area-% Compound 6, relative to the concentration of pridopidine.
 27. The process of claim 13, wherein the pridopidine drug product comprises: i) an amount of Compound 2 in the pridopidine drug substance that is not more than 0.15 area-% Compound 2, relative to the concentration of pridopidine, or ii) an amount of Compound 3 in the pridopidine drug substance that is not more than 0.15 area-% Compound 3, relative to the concentration of pridopidine, or iii) an amount of Compound 5 in the pridopidine drug substance that is not more than 0.15 area-% Compound 5, relative to the concentration of pridopidine, or iv) an amount of Compound 6 in the pridopidine drug substance that is not more than 0.15 area-% Compound 6, relative to the concentration of pridopidine.
 28. The process of claim 15, further comprising: a) determining the amount of at least one of 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfonyl)phenyl)piperidone (hereinafter Compound 2), 1,4-bis((3-(1-propylpiperidin-4-yl)phenyl)sulfonyl)butane (hereinafter Compound 3), 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine 1-oxide (hereinafter Compound 5), or 1-(2-methylpentyl)-4-(3-(methysulfonyl)phenyl)piperidine (hereinafter Compound 6); and b) validating the batch for distribution only if i) the batch is determined to have not more than 0.15 area-% Compound 2, relative to the concentration of pridopidine, or ii) the batch is determined to have not more than 0.15 area-% Compound 3, relative to the concentration of pridopidine, or iii) the batch is determined to have not more than 0.15 area-% Compound 5, relative to the concentration of pridopidine, or iv) the batch is determined to have not more than 0.15 area-% Compound 6, relative to the concentration of pridopidine. 